即时通讯的作用是我使用EMBEDDED LAYOUT在Google Glass中使用CardScrollView插入卡片,因为表格布局在Card Builder中尚不可用。假设每个表都有1个textView。发生的是,当我插入1-3布局时,没有任何错误,但是当我插入第4个布局时,在此行中给了我java.lang.NullPointerException。
tv4.setText('Value for table 4');
这是我的代码:
注意:我在每个表中至少有5个TextView。在这里使其简单。
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
createCards();
mCardScrollView = new CardScrollView(this);
mAdapter = new ExampleCardScrollAdapter();
mCardScrollView.setAdapter(mAdapter);
mCardScrollView.activate();
setContentView(mCardScrollView);
TextView tv1 = (TextView) findViewById(R.id.textView1);
TextView tv2 = (TextView) findViewById(R.id.textView2);
TextView tv3 = (TextView) findViewById(R.id.textView3);
TextView tv4 = (TextView) findViewById(R.id.textView4);
tv1.setText('Value for table 1');
tv2.setText('Value for table 2');
tv3.setText('Value for table 3');
tv4.setText('Value for table 4');
}
private void createCards(){
mCards = new ArrayList<CardBuilder>();
mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
.setEmbeddedLayout(R.layout.activity_layout1)
.setFootnote("TABLE 1"));
mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
.setEmbeddedLayout(R.layout.activity_layout2)
.setFootnote("TABLE 2"));
mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
.setEmbeddedLayout(R.layout.activity_layout3)
.setFootnote("TABLE 3"));
mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
.setEmbeddedLayout(R.layout.activity_layout4)
.setFootnote("TABLE 4"));
}
private class ExampleCardScrollAdapter extends CardScrollAdapter {
@Override
public int getPosition(Object item) {
return mCards.indexOf(item);
}
@Override
public int getCount() {
return mCards.size();
}
@Override
public Object getItem(int position) {
return mCards.get(position);
}
@Override
public int getViewTypeCount() {
return CardBuilder.getViewTypeCount();
}
@Override
public int getItemViewType(int position){
return mCards.get(position).getItemViewType();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
return mCards.get(position).getView(convertView, parent);
}
}
activity_layout1
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TableRow>
<TextView
android:padding="3dip"
android:textSize="20sp"
android:text="@string/textViewTitle1"
android:textColor="@color/muted" />
<TextView
android:id="@+id/textView1"
android:gravity="right"
android:padding="3dip"
android:textSize="20sp" />
</TableRow>
</TableLayout>
activity_layout2
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TableRow>
<TextView
android:padding="3dip"
android:textSize="20sp"
android:text="@string/textViewTitle2"
android:textColor="@color/muted" />
<TextView
android:id="@+id/textView2"
android:gravity="right"
android:padding="3dip"
android:textSize="20sp" />
</TableRow>
</TableLayout>
activity_layout3
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TableRow>
<TextView
android:padding="3dip"
android:textSize="20sp"
android:text="@string/textViewTitle4"
android:textColor="@color/muted" />
<TextView
android:id="@+id/textView3"
android:gravity="right"
android:padding="3dip"
android:textSize="20sp" />
</TableRow>
</TableLayout>
activity_layout4
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TableRow>
<TextView
android:padding="3dip"
android:textSize="20sp"
android:text="@string/textViewTitle4"
android:textColor="@color/muted" />
<TextView
android:id="@+id/textView4"
android:gravity="right"
android:padding="3dip"
android:textSize="20sp" />
</TableRow>
</TableLayout>
适配器
private class ExampleCardScrollAdapter extends CardScrollAdapter {
@Override
public int getPosition(Object item) {
return mCards.indexOf(item);
}
@Override
public int getCount() {
return mCards.size();
}
@Override
public Object getItem(int position) {
return mCards.get(position);
}
@Override
public int getViewTypeCount() {
return CardBuilder.getViewTypeCount();
}
@Override
public int getItemViewType(int position){
return mCards.get(position).getItemViewType();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
return mCards.get(position).getView(convertView, parent);
}
}
请帮忙,因为我在这里待了几天。谢谢!
最佳答案
您为各种视图设置文本的方式有些错误。
为什么崩溃
之所以崩溃,是因为CardScrollView
当前一次检索5个Views
,当前任一方向检索2个。由于CardScrollView
从位置0开始,因此仅加载位置0、1和2处的Views
:这使得可以为tv1
,tv2
和tv2
设置文本,因为它们在视图层次结构中。
由于尚未添加tv4
,因此尝试检索View
将返回null
。
如何解决这个问题
由于CardScrollView
中的每个卡都具有相同的布局,因此您无需创建4个单独的卡并在onCreate
中对其进行初始化。相反,应在需要时为Views
充气,并适当设置文本或其他数据。card_layout.xml
:
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TableRow>
<TextView
android:padding="3dip"
android:textSize="20sp"
android:text="@string/textViewTitle"
android:textColor="@color/muted" />
<TextView
android:id="@+id/textView"
android:gravity="right"
android:padding="3dip"
android:textSize="20sp" />
</TableRow>
</TableLayout>
Adapter
:private class ExampleCardScrollAdapter extends CardScrollAdapter {
@Override
public int getPosition(Object item) {
return mTexts.indexOf(item);
}
@Override
public int getCount() {
return mTexts.size();
}
@Override
public Object getItem(int position) {
return mTexts.get(position);
}
@Override
public int getViewTypeCount() {
return 1;
}
@Override
public int getItemViewType(int position){
return CardBuilder.EMBED_INSIDE.ordinal();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
.setEmbeddedLayout(R.layout.card_layout)
.setFootnote("TABLE " + position)
.getView(convertView, parent);
TextView textView = view.findViewById(R.id.textView);
textView.setText(mTexts.get(position));
return view;
}
}
然后,在您的
Activity
中:protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
createTexts();
mCardScrollView = new CardScrollView(this);
mAdapter = new ExampleCardScrollAdapter();
mCardScrollView.setAdapter(mAdapter);
mCardScrollView.activate(); // This should be moved in onResume.
setContentView(mCardScrollView);
}
private void createTexts(){
mTexts = new ArrayList<String>();
mTexts.add("Value for table 1");
mTexts.add("Value for table 2");
mTexts.add("Value for table 3");
mTexts.add("Value for table 4");
}