从主要活动单击图像视图以切换到第二个活动时
当我实现回收视图之前，我可以切换到第二个活动。
我猜测布局管理器存在某种问题。
activity_second.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
HomeItemAdapter.java
public class HomeItemAdapter extends RecyclerView.Adapter<HomeItemAdapter.ViewHolder> {
private static final String TAG = "NTR-HomeItemAdapter";
// private String[] mDataSet;
public ArrayList<HashMap<String, String>> mDataSource;
private Context mContext;
public HomeItemAdapter(Context context, ArrayList<HashMap<String, String>> mDataSource) {
this.mDataSource = mDataSource;
this.mContext = context;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.row_home_item, viewGroup, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(final ViewHolder viewHolder, int position) {
Target target;
Log.d(TAG, "Element " + position + " set.");
viewHolder.getName().setText(mDataSource.get(position).get("name"));
viewHolder.getCity().setText(mDataSource.get(position).get("city"));
//Get Marquee
viewHolder.getName().setSingleLine();
viewHolder.getName().setEllipsize(TextUtils.TruncateAt.MARQUEE);
viewHolder.getName().setHorizontallyScrolling(true);
viewHolder.getName().setFocusableInTouchMode(true);
viewHolder.getName().setSelected(true);
viewHolder.getName().setMarqueeRepeatLimit(-1);
viewHolder.getCity().setSingleLine();
viewHolder.getCity().setEllipsize(TextUtils.TruncateAt.MARQUEE);
viewHolder.getCity().setHorizontallyScrolling(true);
viewHolder.getCity().setFocusableInTouchMode(true);
viewHolder.getCity().setSelected(true);
viewHolder.getCity().setMarqueeRepeatLimit(-1);
// Get Dynamic Color
target = new com.squareup.picasso.Target() {
@Override
public void onBitmapLoaded(final Bitmap bitmap, Picasso.LoadedFrom from) {
Palette.generateAsync(bitmap, new Palette.PaletteAsyncListener() {
public void onGenerated(Palette palette) {
if (palette !=null) {
viewHolder.getImageCover().setImageBitmap(bitmap);
Palette.Swatch vibrant = palette.getVibrantSwatch();
if(vibrant!=null) {
viewHolder.getCardItemHome().setBackgroundColor(vibrant.getRgb());
viewHolder.getName().setTextColor(vibrant.getTitleTextColor());
viewHolder.getCity().setTextColor(vibrant.getTitleTextColor());
}
}
}
});
}
@Override
public void onBitmapFailed(Drawable errorDrawable) {
viewHolder.getImageCover().setImageResource(R.drawable.cover);
}
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {
}
};
Log.d(TAG,mDataSource.get(position).get("image_url"));
Picasso.with(mContext)
.load(mDataSource.get(position).get("image_url"))
.into(target);
}
@Override
public int getItemCount() {
return mDataSource.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder {
private final CardView cardItemHome;
private final ImageView imgCover;
private final TextView txtName;
private final TextView txtCity;
public ViewHolder(View v) {
super(v);
// Define click listener for the ViewHolder's View.
v.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Element " + getPosition() + " clicked.");
}
});
cardItemHome = (CardView) v.findViewById(R.id.card_item_home);
txtName = (TextView) v.findViewById(R.id.txt_name);
txtCity = (TextView) v.findViewById(R.id.txt_city);
imgCover = (ImageView) v.findViewById(R.id.img_cover);
}
public CardView getCardItemHome() {
return cardItemHome;
}
public TextView getName() {
return txtName;
}
public TextView getCity() {
return txtCity;
}
public ImageView getImageCover() {
return imgCover;
}
}
}
SecondActivity.java
public class SecondActivity extends ActionBarActivity {
public ArrayList<HashMap<String, String>> mDataSource;
protected RecyclerView mRecyclerView;
protected RecyclerView.LayoutManager mLayoutManager;
protected HomeItemAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Initialize Data Source
initDataset();
// BEGIN_INCLUDE(initializeRecyclerView)
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
//The LayoutManager defines how elements are laid out.
mLayoutManager = new GridLayoutManager(this, 3);
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new HomeItemAdapter(this, mDataSource);
// Set CustomAdapter as the adapter for RecyclerView.
mRecyclerView.setAdapter(mAdapter);
// END_INCLUDE(initializeRecyclerView)
}
private void initDataset() {
mDataSource = new ArrayList();
HashMap<String, String> h1 = new HashMap();
h1.put("name", "FIFTH HARMONY");
h1.put("city", "Reflection");
h1.put("image_url","http://www.azlyrics.com/hot/fifthharmony_B00MS4BUUU.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "PAPA ROACH");
h1.put("city", "F.E.A.R.");
h1.put("image_url","http://www.azlyrics.com/hot/919y0earTjL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "Ellie Goulding");
h1.put("city", "ドラえもん");
h1.put("image_url","http://cdn1.umg3.net/12/files/2013/07/EG_HD_stan.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "SAYWECANFLY");
h1.put("city", "Between The Roses");
h1.put("image_url","http://www.azlyrics.com/hot/61-TWobzipL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "NE-YO");
h1.put("city", "Non-Fiction");
h1.put("image_url","http://www.azlyrics.com/hot/81kBXMLAHkL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "Frozen");
h1.put("city", "Frozen Heart Lyrics");
h1.put("image_url","http://www.stlyrics.com/images/ama/frozen_6430.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "2NE1");
h1.put("city", "K-Pop Superstar");
h1.put("image_url","http://www.billboard.com/files/styles/promo_310/public/media/cl_2ne1_instagram_kpop2014_650-430a.png");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "PAPA ROACH");
h1.put("city", "F.E.A.R.");
h1.put("image_url","http://www.azlyrics.com/hot/919y0earTjL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "SAYWECANFLY");
h1.put("city", "Between The Roses");
h1.put("image_url","http://www.azlyrics.com/hot/61-TWobzipL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "NE-YO");
h1.put("city", "Non-Fiction");
h1.put("image_url","http://www.azlyrics.com/hot/81kBXMLAHkL.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "Frozen");
h1.put("city", "Frozen Heart Lyrics");
h1.put("image_url","http://www.stlyrics.com/images/ama/frozen_6430.jpg");
mDataSource.add(h1);
h1 = new HashMap();
h1.put("name", "2NE1");
h1.put("city", "K-Pop Superstar");
h1.put("image_url","http://www.billboard.com/files/styles/promo_310/public/media/cl_2ne1_instagram_kpop2014_650-430a.png");
mDataSource.add(h1);
}
}
日志猫
Process: com.example.sensei.mist, PID: 2193
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sensei.mist/com.example.sensei.mist.SecondActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.example.sensei.mist.SecondActivity.onCreate(SecondActivity.java:33)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
最佳答案
在SecondActivity中，更改
setContentView(R.layout.activity_main);
至
setContentView(R.layout.activity_second);