我在视图寻呼机内有一个表面视图时遇到问题。一切正常，直到我按其中一个选项卡。视图寻呼机滚动，但下一个屏幕上的页面被压缩。
如果我退出该应用程序并返回其中，则第二页会很好。然后，如果我按返回到第一个，它将再次被挤压。
我完全不知道布局的哪一部分出了问题，据我所知，表面视图的实际高度没有改变，就像我在表面视图上使用.getHeight（）方法时一样总是返回相同的值。
这是我的视图寻呼机类：
public class PendulumViewPager extends ViewPager {
public PendulumViewPager(Context context) {
super(context);
}
public PendulumViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
return false;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return false;
}
这是添加到视图分页器中的片段：
public class SurfacePanelFragment extends Fragment{
private int TYPE = 1;
private SurfacePanel panel;
public void setType(int type){
TYPE = type;
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_surface_panel, container, false);
panel = view.findViewById(R.id.canvas);
panel.setType(TYPE);
return view;
}
public void startStopPendulum(ImageButton view){
panel.startStop(view);
}
public void stopPendulum(){
panel.stop();
}
@Override
public void onResume() {
if(getUserVisibleHint()) {
panel.delayStartThread();
((MainActivity)getActivity()).getStopButton().setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_pause_white_48dp));
}
super.onResume();
}
@Override
public void onPause() {
panel.terminate();
super.onPause();
}
public void stopRendering(){
panel.stopRendering();
}
public void startRendering(){
panel.startRendering();
}
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if(panel != null) {
if (isVisibleToUser) {
panel.delayStartThread();
((MainActivity)getActivity()).getStopButton().setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_pause_white_48dp));
Log.i("WP", String.valueOf(panel.getHeight()));
} else {
panel.terminate();
}
}
}
这是主要活动：
public class MainActivity extends AppCompatActivity {
private PendulumViewPager pager;
private ArrayList<SurfacePanelFragment> fragments = new ArrayList<SurfacePanelFragment>(2);
private ImageButton stopButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);
pager = findViewById(R.id.view_pager);
pager.setAdapter(new FragmentStatePagerAdapter(getSupportFragmentManager()) {
@Override
public Fragment getItem(int position) {
SurfacePanelFragment frag = new SurfacePanelFragment();
switch (position) {
case 0:
frag.setType(SurfacePanel.SINGLE_PENDULUM);
fragments.add(0, frag);
return frag;
case 1:
frag.setType(SurfacePanel.DOUBLE_PENDULUM);
fragments.add(1, frag);
return frag;
default:
return null;
}
}
@Override
public int getCount() {
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0: return "Single";
case 1: return "Double";
default: return "";
}
}
});
TabLayout pagerTabs = findViewById(R.id.pager_tabs);
pagerTabs.setTabGravity(TabLayout.GRAVITY_FILL);
pagerTabs.setupWithViewPager(pager);
stopButton = findViewById(R.id.stop_button);
stopButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startStopCurrentPendulum((ImageButton) view);
}
});
ImageButton helpButton = findViewById(R.id.help_button);
helpButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startHelpActivity();
}
});
}
private void startStopCurrentPendulum(ImageButton view) {
fragments.get(pager.getCurrentItem()).startStopPendulum(view);
}
public ImageButton getStopButton(){
return stopButton;
}
private void startHelpActivity(){
Intent intent = new Intent(this, HelpActivity.class);
startActivity(intent);
}
这是SurfacePanel类
public class SurfacePanel extends SurfaceView implements SurfaceHolder.Callback {
public static final int SINGLE_PENDULUM = 1;
public static final int DOUBLE_PENDULUM = 2;
private int TYPE = 1;
private PendulumThread _thread;
private boolean needToStartThread = false;
private SurfaceHolder holder;
public SurfacePanel(Context context, AttributeSet attrSet) {
super(context, attrSet);
SurfaceHolder holder = getHolder();
holder.addCallback(this);
}
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
Log.i("WP", String.valueOf(this.getHeight()));
this.holder = surfaceHolder;
if(needToStartThread){
startThread();
needToStartThread = false;
}
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
if(_thread != null) {
try {
_thread.terminate();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.holder = null;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (_thread != null) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
_thread.click(event);
} else if (event.getAction() == MotionEvent.ACTION_MOVE) {
_thread.updatePos(event);
} else if (event.getAction() == MotionEvent.ACTION_UP) {
_thread.unclick();
}
}
return true;
}
public void startStop(ImageView button) {
if(_thread != null){
if(_thread.isPRunning()){
button.setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_play_arrow_white_48dp));
_thread.pStop();
}else{
button.setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_pause_white_48dp));
_thread.pStart();
}
}
}
public void start(){
if(_thread != null){
_thread.pStart();
}
}
public void stop(){
if(_thread != null){
_thread.pStop();
}
}
public void stopRendering(){
if(_thread != null){
Log.i("WP", "A");
_thread.stopRendering();
}
}
public void startRendering(){
if(_thread != null){
Log.i("WP", "D");
_thread.startRendering();
}
}
public void terminate(){
if(_thread != null){
try {
_thread.terminate();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void startThread(){
if(_thread == null || !_thread.isAlive()) {
switch (TYPE) {
case SurfacePanel.SINGLE_PENDULUM:
_thread = new SinglePendulumThread(holder, getWidth(), getHeight(), getContext());
_thread.pStart();
_thread.start();
break;
case SurfacePanel.DOUBLE_PENDULUM:
_thread = new DoublePendulumThread(holder, getWidth(), getHeight(), getContext());
_thread.pStart();
_thread.start();
break;
default:
_thread = new SinglePendulumThread(holder, getWidth(), getHeight(), getContext());
_thread.pStart();
_thread.start();
break;
}
}
}
public void delayStartThread(){
if(holder == null) {
needToStartThread = true;
}else{
startThread();
}
}
public void setType(int type){
TYPE = type;
}
这是带有面板视图的面板片段
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<com.astarphysics.wikidpendulum.SurfacePanel
android:id="@+id/canvas"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:layout_editor_absoluteX="8dp"
tools:layout_editor_absoluteY="8dp" />
</RelativeLayout>
这是单摆线
public class SinglePendulumThread extends PendulumThread{
private SurfaceHolder holder;
private Paint paint;
private int backgroundColor;
private int width;
private Context context;
private boolean clicked = false;
private static final double g = 9.81;
private final int RADIUS;
private int length;
private double theta = Math.PI/8;
private double thetaV = 0;
SinglePendulumThread(SurfaceHolder holder, int width, int height, Context context){
this.holder = holder;
this.context = context;
int bobColor = context.getResources().getColor(R.color.colorBob);
int shadowColor = context.getResources().getColor(R.color.shadowColor);
backgroundColor = context.getResources().getColor(R.color.backgroundColor);
paint = new Paint();
paint.setColor(bobColor);
paint.setShadowLayer(5, -1, 2, shadowColor);
this.width = width;
RADIUS = dpToPx(20);
length = dpToPx(200);
}
protected void update(){
if(pRunning && !clicked) {
thetaV += (-1 * g * Math.sin(theta)) / length;
theta += thetaV * (40 * Math.pow(10, -2));
}
}
protected void render(){
Canvas canvas = holder.lockCanvas();
canvas.drawColor(backgroundColor);
canvas.drawLine(width / 2, 0, (float) ((width / 2) + (length * Math.sin(theta))), (float) (length * Math.cos(theta)), paint);
canvas.drawCircle((int) Math.round((width / 2) + (length * Math.sin(theta))), (int) Math.round(length * Math.cos(theta)), RADIUS, paint);
holder.unlockCanvasAndPost(canvas);
}
@Override
void click(MotionEvent e) {
clicked = true;
updatePos(e);
}
@Override
void updatePos(MotionEvent e){
length = (int)Math.round(Math.sqrt((Math.abs(e.getX()-(width/2))*Math.abs(e.getX()-(width/2)))+(e.getY()*e.getY())));
theta = Integer.signum(Math.round((e.getX()-(width/2))))*Math.asin((Math.abs(e.getX()-(width/2))/length));
}
@Override
void unclick() {
this.resetForPStart();
clicked = false;
}
private void resetForPStart(){
thetaV = 0;
}
private int dpToPx(int dp) {
DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
return Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT));
}
这是双摆线：
public class DoublePendulumThread extends PendulumThread {
private SurfaceHolder holder;
private Paint paint;
private int backgroundColor;
private int width;
private int height;
private Context context;
private boolean clicked1 = false;
private boolean clicked2 = false;
private final int RADIUS;
private final double m1 = 3;
private final double m2 = 3;
private static final double g = 9.81;
private double l1;
private double l2;
private double[] state = new double[4];
private double[] dydt = new double[4];
private double[] prev = new double[4];
private double[] midpt = new double[4];
private static final double h = 0.5;
private static final double DIMENSION = 4;
private static final double HALF = h/2;
private static final double THIRD = h/3;
private static final double SIXTH = h/6;
DoublePendulumThread(SurfaceHolder holder, int width, int height, Context context){
this.holder = holder;
this.context = context;
this.width = width;
this.height = height;
//Setting sizes that require Context to be set
RADIUS = dpToPx(20);
l1 = dpToPx(150);
l2 = dpToPx(150);
state[0] = Math.PI/8;
//Setting up paints for rendering on Canvas
int bobColor = context.getResources().getColor(R.color.colorBob);
int shadowColor = context.getResources().getColor(R.color.shadowColor);
backgroundColor = context.getResources().getColor(R.color.backgroundColor);
paint = new Paint();
paint.setColor(bobColor);
paint.setShadowLayer(5, -1, 2, shadowColor);
}
/*
Evaluates derivatives for Runge-Kutta.
*/
private void loadDys(double[] y){
dydt[0] = y[2]; //Theta1
dydt[1] = y[3]; //Theta2
dydt[2] = ( -1*g*(2*m1 + m2)*sin(y[0]) - m2*g*sin(y[0] - 2*y[1]) - 2*sin(y[0] - y[1])*m2*(y[3]*y[3]*l2 + y[2]*y[2]*l1*cos(y[0] - y[1])) ) / (l1*(2*m1 + m2 - m2*cos(2*y[0]-2*y[1])));
dydt[3] = (2*sin(y[0] - y[1])*(y[2]*y[2]*l1*(m1+m2) + g*(m1+m2)*cos(y[0]) + y[3]*y[3]*l2*m2*cos(y[0]-y[1]))) / (l2*(2*m1 + m2 - m2*cos(2*y[0]-2*y[1])));
}
/*
Each time update is run one iteration of the Runge-Kutta method takes place, with time step h.
*/
protected void update(){
if(pRunning && !clicked1 && !clicked2) {
for (int i = 0; i < DIMENSION; i++) {
midpt[i] = state[i];
prev[i] = state[i];
}
loadDys(midpt);
for (int i = 0; i < DIMENSION; i++) {
state[i] += SIXTH * dydt[i];
midpt[i] = prev[i] + HALF * dydt[i];
}
loadDys(midpt);
for (int i = 0; i < DIMENSION; i++) {
state[i] += THIRD * dydt[i];
midpt[i] = prev[i] + HALF * dydt[i];
}
loadDys(midpt);
for (int i = 0; i < DIMENSION; i++) {
state[i] += THIRD * dydt[i];
midpt[i] = prev[i] + h * dydt[i];
}
loadDys(midpt);
for (int i = 0; i < DIMENSION; i++) {
state[i] += SIXTH * dydt[i];
}
}else if(pRunning && clicked1) {
state[3] += (-1 * g * Math.sin(state[1])) / l2;
state[3] = state[3] * 0.9;
state[1] += state[3] * (40 * Math.pow(10, -2));
}
}
protected void render(){
Canvas canvas = holder.lockCanvas();
canvas.drawColor(backgroundColor);
canvas.drawLine(width / 2, height/4, (float) ((width / 2) + (l1 * Math.sin(state[0]))), (float) (height/4 + l1 * Math.cos(state[0])), paint);
canvas.drawLine((float) ((width / 2) + (l1 * Math.sin(state[0]))), (float) (height/4 + l1 * Math.cos(state[0])), (float) ((width / 2) + (l1 * Math.sin(state[0])) + (l2 * Math.sin(state[1]))), (float) (height/4 + l1 * Math.cos(state[0]) + l2 * Math.cos(state[1])), paint);
canvas.drawCircle((float) ((width / 2) + (l1 * Math.sin(state[0]))), (float) (height/4 + l1 * Math.cos(state[0])), RADIUS, paint);
canvas.drawCircle((float) ((width / 2) + (l1 * Math.sin(state[0])) + (l2 * Math.sin(state[1]))), (float) (height/4 + l1 * Math.cos(state[0]) + l2 * Math.cos(state[1])), RADIUS, paint);
holder.unlockCanvasAndPost(canvas);
}
void updatePos(MotionEvent e){
if(clicked1){
l1 = (int)Math.round(Math.sqrt(((e.getX()-(width/2))*(e.getX()-(width/2)))+((e.getY()-height/4)*(e.getY()-height/4))));
if(e.getY() - height/4 < 0) {
if (Math.round(e.getX() - width / 2) == 0) {
state[0] = Math.PI;
} else {
state[0] = Integer.signum(Math.round((e.getX() - (width / 2)))) * Math.acos((Math.abs(e.getX() - (width / 2)) / l1)) + Integer.signum(Math.round((e.getX() - (width / 2)))) * Math.PI / 2;
}
}else if(Math.round(e.getY() - (height/4)) == 0){
state[0] = Integer.signum(Math.round(e.getX() - (width/2))) * Math.PI / 2;
}else{
state[0] = Math.asin((e.getX()-(width/2))/l1);
}
}else if(clicked2){
l2 = (int)Math.round(Math.sqrt(((e.getX()-((width / 2) + (l1 * Math.sin(state[0]))))*(e.getX()-((width / 2) + (l1 * Math.sin(state[0])))))+((e.getY()-(height/4 + l1 * Math.cos(state[0])))*(e.getY()-(height/4 + l1 * Math.cos(state[0]))))));
if(e.getY() - (height/4 + l1 * Math.cos(state[0])) < 0){
if(Math.round(e.getX() - ((width/2) + l1*sin(state[0]))) == 0){
state[1] = Math.PI;
}else {
state[1] = Integer.signum((int) Math.round((e.getX() - ((width / 2) + (l1 * Math.sin(state[0])))))) * Math.acos((Math.abs(e.getX() - ((width / 2) + (l1 * Math.sin(state[0])))) / l2)) + Integer.signum((int) Math.round((e.getX() - ((width / 2) + (l1 * Math.sin(state[0])))))) * Math.PI / 2;
}
}else if(Math.round(e.getY() - (height/4 + l1 * Math.cos(state[0]))) == 0) {
state[1] = Integer.signum((int) Math.round(e.getX() - ((width/2) + l1*sin(state[0])))) * Math.PI / 2;
}else{
state[1] = Math.asin((e.getX()-((width / 2) + (l1 * Math.sin(state[0]))))/l2);
}
}
}
void click(MotionEvent e){
if((e.getX() - ((width / 2) + (l1 * Math.sin(state[0])) + (l2 * Math.sin(state[1]))))*(e.getX() - ((width / 2) + (l1 * Math.sin(state[0])) + (l2 * Math.sin(state[1])))) + (e.getY() - (height/4 + l1 * Math.cos(state[0]) + l2 * Math.cos(state[1])))*(e.getY() - (height/4 + l1 * Math.cos(state[0]) + l2 * Math.cos(state[1]))) <= RADIUS*RADIUS){
clicked2 = true;
}else {
clicked1 = true;
}
updatePos(e);
}
void unclick(){
if(clicked1 || clicked2) {
state[2] = 0;
state[3] = 0;
for (int i = 0; i < DIMENSION; i++) {
dydt[i] = 0;
midpt[i] = 0;
prev[i] = 0;
}
clicked1 = false;
clicked2 = false;
}
}
private int dpToPx(int dp) {
DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
return Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT));
}
private static double sin(double x){
return Math.sin(x);
}
private static double cos(double x){
return Math.cos(x);
}
这是将片段嵌入到视图分页器中的主要活动。
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/. apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.astarphysics.wikidpendulum.MainActivity"
>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<com.astarphysics.wikidpendulum.PendulumViewPager
android:id="@+id/view_pager"
android:layout_width="0dp"
android:layout_height="0dp"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
tools:layout_constraintBottom_creator="1"
android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_marginEnd="8dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="8dp"
tools:layout_constraintLeft_creator="1"
android:layout_marginBottom="8dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp">
</com.astarphysics.wikidpendulum.PendulumViewPager>
</android.support.constraint.ConstraintLayout>
<android.support.design.widget.AppBarLayout
android:layout_height="wrap_content"
android:layout_width="match_parent">
<android.support.v7.widget.Toolbar
app:layout_scrollFlags="enterAlways"
android:id="@+id/toolbar"
android:layout_height="192dp"
android:layout_width="match_parent"
app:contentInsetLeft="0dp"
app:contentInsetStart="0dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="144dp">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:padding="10dp">
<android.support.v7.widget.AppCompatImageButton
android:id="@+id/stop_button"
android:layout_width="48dp"
android:layout_height="48dp"
app:srcCompat="@drawable/ic_pause_white_48dp"
android:background="?attr/selectableItemBackgroundBorderless"
android:layout_marginRight="10dp"
android:layout_marginEnd="10dp"/>
<android.support.v7.widget.AppCompatImageButton
android:id="@+id/help_button"
android:layout_width="48dp"
android:layout_height="48dp"
app:srcCompat="@drawable/ic_help_white_48dp"
android:background="?attr/selectableItemBackgroundBorderless" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:layout_width="80dp"
android:layout_height="80dp"
android:src="@drawable/icon"/>
<TextView
android:layout_width="150dp"
android:layout_height="wrap_content"
android:text="@string/app_name"
android:gravity="center"
android:textSize="24sp"
android:fontFamily="sans-serif-smallcaps"
android:textColor="@color/textColor"/>
</LinearLayout>
</RelativeLayout>
<android.support.design.widget.TabLayout
android:id="@+id/pager_tabs"
android:layout_width="match_parent"
android:layout_height="48dp">
</android.support.design.widget.TabLayout>
</LinearLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>
如果您认为还有其他问题，可以添加代码。
谢谢。
最佳答案
只需更改ViewPager中的页面并不会迫使片段经历其生命周期，也不会导致重新创建SurfaceView。按下recents或home然后返回应用程序确实会导致重新创建SurfaceView，这似乎可以纠正您所看到的问题。
如果问题是与您的布局有关的细微问题，我建议您尽可能简化它。我重新设计了两个主要布局以简化它们，如下所示。如果您决定走这条路线，则可能需要在主布局中进行一些更改，以按所需的方式调整大小/位置。您不必进行任何结构上的更改。
如果上述方法不起作用，可以尝试的另一种方法是在API 26+中选择该片段时强制重新创建该片段。这将迫使重新实例化片段和布局，并应纠正问题。
如果新布局有效，那将是最好的；如果必须在选择选项卡时重新创建，那只是一种解决方法。如果您发现根本问题是什么，请在此处发布。我会对知道它是什么感兴趣。也许对此问题的另一位读者可以深入探讨。
pendulum_layout.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="144dp"
app:contentInsetLeft="0dp"
app:contentInsetStart="0dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:padding="10dp">
<android.support.v7.widget.AppCompatImageButton
android:id="@+id/stop_button"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_marginEnd="10dp"
android:layout_marginRight="10dp"
android:background="?attr/selectableItemBackgroundBorderless"
app:srcCompat="@drawable/ic_pause_white_48dp" />
<android.support.v7.widget.AppCompatImageButton
android:id="@+id/help_button"
android:layout_width="48dp"
android:layout_height="48dp"
android:background="?attr/selectableItemBackgroundBorderless"
app:srcCompat="@drawable/ic_help_white_48dp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:layout_width="80dp"
android:layout_height="80dp"
android:src="@drawable/icon" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:fontFamily="sans-serif-smallcaps"
android:gravity="center"
android:text="@string/app_name"
android:textColor="#FF000000"
android:textSize="24sp" />
</LinearLayout>
</RelativeLayout>
</android.support.v7.widget.Toolbar>
<com.example.viewpagerbase.PendulumViewPager
android:id="@+id/view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.TabLayout
android:id="@+id/pager_tabs"
android:layout_width="match_parent"
android:layout_height="48dp" />
</com.example.viewpagerbase.PendulumViewPager>
</LinearLayout>
fragment_main.xml
<com.example.viewpagerbase.MySurfaceView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/surfaceView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
这是选择新片段时强制使用的一种方法。如果您搜索其他在线方法，也可以使用它们。
将以下内容添加到您的
ViewPager中，并从每个构造函数中调用。这将为API 26+设置页面监听器。每当选择其他页面时，该监听器就会触发。private void init() {
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
return;
}
addOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
MainActivity.SectionsPagerAdapter adapter =
// Your adapter name goes here
((MainActivity.SectionsPagerAdapter) getAdapter());
adapter.invalidateFragment(position);
}
@Override
public void onPageScrollStateChanged(int position) {
}
});
}
将以下内容添加到您的适配器：
private List<SurfacePanelFragment> fragments = new ArrayList<>(PAGE_COUNT);
@Override
public SurfacePanelFragment getItem(int position) {
if (fragments.get(position) == null) {
fragments.set(position, SurfacePanelFragment.newInstance());
}
return fragments.get(position);
}
@Override
public int getItemPosition(Object object) {
return (fragments.contains(object)) ? POSITION_UNCHANGED : POSITION_NONE;
}
public void invalidateFragment(int position) {
fragments.set(position, null);
notifyDataSetChanged();
}
private static final int PAGE_COUNT = 2;