android - 为什么在尝试在 ScrollView 中单击按钮时设置 EditText 时会出现 Nullpointer 异常？

Question

我有一个 ScrollView，它有一个固定的页眉和页脚。我在我的类(class)中实现了 onClickListener。单击按钮时，我试图在 EditText 中设置文本。但是当我这样做时，我得到了一个Nullpointer Exception。

我的代码如下:

内容.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical" >

<EditText
    android:id="@+id/editText04"
    android:layout_width="190dp"
    android:layout_height="23dp"
    android:layout_alignBaseline="@+id/textView2"
    android:layout_alignBottom="@+id/textView2"
    android:layout_alignParentRight="true"
    android:layout_marginRight="5dp"
    android:background="@drawable/roundedittext"
    android:ems="10"
    android:paddingLeft="25dp"
    android:text="Task 1"
    android:textColor="#FFFFFF"
    android:textSize="17dp" >

    <requestFocus />
</EditText> 
</RelativeLayout>

可滚动内容.xml

<?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:layout_width="match_parent"
 android:layout_height="match_parent" >

  <!-- Header aligned to top -->

 <RelativeLayout
  android:id="@+id/header"
  android:layout_width="match_parent"
  android:layout_height="70dp"
  android:layout_alignParentTop="true"
   android:background="@android:color/white"  >

  <ImageView
      android:id="@+id/imageView1"
      android:layout_width="50dp"
      android:layout_height="50dp"
      android:layout_alignParentLeft="true"
      android:layout_centerVertical="true"
      android:layout_marginLeft="18dp"
      android:src="@drawable/propic" />

  <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerVertical="true"
      android:layout_marginLeft="24dp"
      android:layout_toRightOf="@+id/imageView1"
      android:text="Jack Reacher"
       android:textSize="17dp" 
      android:textColor="#000" />
  </RelativeLayout>

  <!-- Footer aligned to bottom -->

 <RelativeLayout
  android:id="@+id/footer"
  android:layout_width="fill_parent"
  android:layout_height="50dp"
  android:layout_alignParentBottom="true"
  android:visibility="visible"
  android:background="@android:color/black" >

  <Button
      android:id="@+id/button1"
      android:layout_width="160dp"
      android:layout_height="50dp"
      android:background="@color/green"
      android:layout_alignParentTop="true"
      android:text="Accept" 
       android:textSize="17dp" 
       android:visibility="visible"
       android:textColor="#FFFFFF"/>

  <Button
      android:id="@+id/button2"
      android:layout_width="160dp"
      android:layout_height="50dp"
       android:textSize="17dp" 
      android:layout_alignParentTop="true"
      android:layout_toRightOf="@+id/button1"
       android:background="@color/red"
      android:text="Decline" 
       android:visibility="visible"
        android:textColor="#FFFFFF"/>

  <Button
      android:id="@+id/button3"
      android:layout_width="112dp"
      android:layout_height="fill_parent"
      android:layout_alignParentBottom="true"
      android:layout_alignParentLeft="true"
      android:text="Completed" 
         android:visibility="gone"
      android:textColor="@android:color/white"
      android:background="@color/green"/>

  <Button
      android:id="@+id/button4"
      android:layout_width="105dp"
      android:layout_height="fill_parent"
      android:layout_alignParentBottom="true"
      android:layout_toRightOf="@+id/button3"
      android:text="Ongoing"
      android:visibility="gone"
       android:textColor="@android:color/white"
      android:background="@color/yellow" />

  <Button
      android:id="@+id/button5"
      android:layout_width="105dp"
      android:background="@color/red"
      android:layout_height="fill_parent"
      android:layout_alignParentBottom="true"
      android:layout_alignParentRight="true"
      android:text="Decline"
      android:visibility="gone"
       android:textColor="@android:color/white" />

  </RelativeLayout>
  <!-- Scrollable Item below header and above footer -->
  <ScrollView
   android:id="@+id/scrollableContents"
  android:layout_width="fill_parent"
   android:layout_height="fill_parent"
  android:layout_above="@id/footer"
  android:background="@android:color/white" 
  android:layout_below="@id/header" >

   <!-- Inflate the contents of the ScrollView dynamicaly -->

 </ScrollView>

 </RelativeLayout>

我的contactstemp.java

 public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    // final Databasehandler2 db=new Databasehandler2(getActivity().getApplicationContext());
    View view = inflater.inflate(R.layout.scrollable_contents, container,
            false);
    ScrollView scrollable_contents = (ScrollView)view.findViewById(R.id.scrollableContents);
    View v2 =getActivity().getLayoutInflater().inflate(R.layout.contents, scrollable_contents);
    EditText stat=(EditText)v2.findViewById(R.id.editText04);
     scrollable_contents.addView(v2);
  return view;
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch(v.getId())
    {
    case R.id.button1:
        Toast.makeText(getActivity(),"accept clicked",1000).show();

        stat.setText("Paused");
        /*b1.setVisibility(v.VISIBLE);
        b2.setVisibility(v.VISIBLE);
        b3.setVisibility(v.VISIBLE);*/
        break;
      }
     }

堆栈跟踪:

    E/AndroidRuntime(5223): FATAL EXCEPTION: main
    E/AndroidRuntime(5223): java.lang.NullPointerException
    E/AndroidRuntime(5223):     at com.example.taskmanager.mycontactstemp.onClick(mycontactstemp.java:106)
    E/AndroidRuntime(5223):     at android.view.View.performClick(View.java:4204)
    E/AndroidRuntime(5223):     at android.view.View$PerformClick.run(View.java:17355)
    E/AndroidRuntime(5223):     at android.os.Handler.handleCallback(Handler.java:725)
    E/AndroidRuntime(5223):     at android.os.Handler.dispatchMessage(Handler.java:92)
    E/AndroidRuntime(5223):     at android.os.Looper.loop(Looper.java:137)
    E/AndroidRuntime(5223):     at android.app.ActivityThread.main(ActivityThread.java:5041)
    E/AndroidRuntime(5223):     at java.lang.reflect.Method.invokeNative(Native Method)
    E/AndroidRuntime(5223):     at java.lang.reflect.Method.invoke(Method.java:511)
    E/AndroidRuntime(5223):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    E/AndroidRuntime(5223):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
   E/AndroidRuntime(5223):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

这个stat是空的

EditText stat=(EditText)view.findViewById(R.id.EditText04)

您膨胀的布局是scrollable_contents.xml

View view = inflater.inflate(R.layout.scrollable_contents, container,
        false);

并且您使用相同的 View 对象来初始化 EditText。

它属于contents.xml。此外，id 是 editText04 而不是 EditText04

并且您正在为 null 的 stat 调用 setText。

stat.setText("Paused");

修复 Inflate 布局

View v= getActivity().getLayoutInflater().inflate(R.layout.contents, scrollable_contents);
stat=(EditText)v.findViewById(R.id.editText04);

最后将这个 View 添加到ScrollView

scrollable_contents.addView(v);

编辑:

改变这个

 EditText stat=(EditText)v2.findViewById(R.id.editText04);

到

 stat=(EditText)v2.findViewById(R.id.editText04);

编辑 2:

我不知道为什么这会被否决

将scrollable_contents.xml改为

<?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:layout_width="match_parent"
    android:layout_height="match_parent" >

    <!-- Header aligned to top -->

    <LinearLayout
        android:id="@+id/header"
        android:layout_width="match_parent"
        android:layout_height="70dp"
        android:orientation="horizontal"
        android:layout_alignParentTop="true"
        android:background="@android:color/white" >

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="50dp"
            android:background="@drawable/ic_launcher"
            android:layout_marginLeft="18dp" />

        <TextView
            android:id="@+id/textView1"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:layout_marginLeft="24dp"
            android:text="Jack Reacher"
            android:textColor="#000"
            android:textSize="17dp" />
    </LinearLayout>

    <!-- Footer aligned to bottom -->

    <LinearLayout
        android:id="@+id/footer"
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:background="@android:color/black"
        android:visibility="visible" >

        <Button
            android:id="@+id/button1"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="50dp"
            android:text="Accept"
            android:textColor="#FFFFFF"
            android:visibility="visible" />

        <Button
            android:id="@+id/button2"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="50dp"
            android:text="Decline"
            android:textColor="#FFFFFF"

            android:visibility="visible" />

        <Button
            android:id="@+id/button3"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="fill_parent"
            android:text="Completed"
            android:textColor="@android:color/white"
            android:visibility="visible" />

        <Button
            android:id="@+id/button4"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="fill_parent"
            android:text="Ongoing"
            android:textColor="@android:color/white"
            android:visibility="visible" />

        <Button
            android:id="@+id/button5"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="fill_parent"
            android:text="Decline"
            android:textColor="@android:color/white"
            android:visibility="visible"  />
    </LinearLayout>
    <!-- Scrollable Item below header and above footer -->

    <ScrollView
        android:id="@+id/sl"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@id/footer"
        android:layout_below="@id/header"
        android:background="@android:color/white" >

    </ScrollView>

</RelativeLayout> 

和contents.xml到

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical" >

<EditText
    android:id="@+id/editText04"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Task 1"
    android:textSize="17sp" >

    <requestFocus />
</EditText> 
</LinearLayout>

将您的 fragment 更改为

public class MyFragment extends Fragment implements OnClickListener {
    EditText stat;
    View view ;
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        view = inflater.inflate(R.layout.scollable_contents, null);

        Button button1 = (Button) view.findViewById(R.id.button1);
        button1.setOnClickListener(this);
        ScrollView scrollable_contents = ( ScrollView)view.findViewById(R.id.sl);
        LinearLayout v2 =(LinearLayout) getActivity().getLayoutInflater().inflate(R.layout.contents, null);
        stat=(EditText)v2.findViewById(R.id.editText04);
        scrollable_contents.addView(v2);

      return view;
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId())
        {
        case R.id.button1:
            Toast.makeText(getActivity(),"accept clicked",1000).show();
            stat.setText("Paused");
            break;
          }
         }  
}

快照

注意:

textSize 使用 sp 而不是 dp。