空指针指向addView

时间：2011-03-07 00:41:53

标签： android view android-fragments

我试图以编程方式将textview添加到线性布局中，但我在线性布局上不断获得空指针。它在布局膨胀后被调用，所以我不明白为什么会发生这种情况。继承人的代码。

tile_layout.xml 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    
android:id="@+id/master"
android:orientation="horizontal"    
android:layout_width="fill_parent"   
android:layout_height="match_parent"> 
<TextView
android:id="@+id/fragment_two_directory"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Testing Fragment Two" />



</LinearLayout>

fragment_two.java 

public class fragment_two extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.tile_layout,container, false);
}

public static fragment_two newInstance(String directory, Activity activity) {
    fragment_two ft = new fragment_two();
    TextView text = (TextView)activity.findViewById(R.id.fragment_two_directory);
    text.setText(directory);
    return ft;
}
public static void setDirectoryText(String directory, Activity activity) {
    TextView directoryText = (TextView)activity.findViewById(R.id.fragment_two_directory);
    directoryText.setText(directory);
    populateDirectory(directory, activity);
}
public static void populateDirectory(String directory, Activity activity) {
    LinearLayout masterLinear = (LinearLayout)activity.findViewById(R.id.master);
    TextView testText = new TextView(activity);
    testText.setText("test");
    masterLinear.addView(testText);
    //testText.setText("Testing Add View");
    //for (int x=0; x < 5; x++) {
        //FrameLayout container = new FrameLayout(getActivity());
        //container.setLayoutParams(new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        //ImageView fileImage = new ImageView(getActivity());
        //fileImage.setLayoutParams(new FrameLayout.LayoutParams(110, 110));
        //fileImage.setImageResource(R.drawable.blank_file);
        //container.addView(fileImage);
        //TextView fileName = new TextView(getActivity());
        //fileName.setLayoutParams(new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        //fileName.setText("Filename.txt");
        //container.addView(fileName);
        //masterLinear.addView(container);
    //}

}
}

最后这是主要的活动

package com.bv.dual_fragments;

import com.bv.dual_fragments.fragment_one.OnArticleSelectedListener;

import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.widget.TextView;

    public class dual_fragments extends Activity implements OnArticleSelectedListener {
    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.test);
        //((global_holder)this.getApplication()).setDirectory("test"); 

    }
    @Override
    public void onArticleSelected(String directory) {
        //fragment_two frag_two = (fragment_two)getFragmentManager().findFragmentById(R.id.container);
        //TextView containerText = (TextView)findViewById(R.id.fragment_two_directory);
        //containerText.setText(directory);
        fragment_two.populateDirectory(directory, this);
    }
}

继承LogCat 

03-06 17:35:47.452: ERROR/AndroidRuntime(3576): FATAL EXCEPTION: main
03-06 17:35:47.452: ERROR/AndroidRuntime(3576): java.lang.NullPointerException
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at     com.bv.dual_fragments.fragment_two.populateDirectory(fragment_two.java:36)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.bv.dual_fragments.dual_fragments.onArticleSelected(dual_fragments.java:25)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.bv.dual_fragments.fragment_one.onListItemClick(fragment_one.java:88)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.app.ListFragment$2.onItemClick(ListFragment.java:160)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.widget.AdapterView.performItemClick(AdapterView.java:282)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.widget.AbsListView.performItemClick(AbsListView.java:1032)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2447)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.widget.AbsListView.onTouchEvent(AbsListView.java:3077)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.widget.ListView.onTouchEvent(ListView.java:3566)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.View.dispatchTouchEvent(View.java:4600)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1488)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1256)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1494)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1269)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1700)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1270)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.app.Activity.dispatchTouchEvent(Activity.java:2271)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1680)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2272)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1958)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.os.Looper.loop(Looper.java:126)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at android.app.ActivityThread.main(ActivityThread.java:3997)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at java.lang.reflect.Method.invokeNative(Native Method)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at java.lang.reflect.Method.invoke(Method.java:491)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
03-06 17:35:47.452: ERROR/AndroidRuntime(3576):     at dalvik.system.NativeStart.main(Native Method)

我也在蜂窝模拟器中运行它，并查看了heirarchy查看器。我在layoutfile中有两个linearlayout，它们都没有出现，只有textview。

3 个答案:

答案 0 :(得分：1)

好吧，问题是布局文件搞砸了，我有两个线性布局，因此heirarchy不会加载它们，给出零点异常。对于任何查看Android 3.0的heirarchyviewer的人来说，这个片段（在layoutfile中）将自动获取其膨胀视图中第一个布局标签的所有权。所以说你有

<fragment android:id="@+id/viewer" />

并在您的布局文件中

<LinearLayout android:id="@+id/first_layout" />

在heirarchy查看器中，LinearLayout将显示为查看器，而不是first_layout，因为片段没有默认布局，它会将布局文件中的第一个布局容器重新标识为自己的id。

答案 1 :(得分：0)

如果您要查找R.id.tile_layout，是否应将内容视图设置为R.id.master？

现在你正在test.xml寻找它。

答案 2 :(得分：0)

你确定在OnCreate（）之后调用了OnArticleSelected（）吗？如果在调用setContentView（layout）之前调用它，findViewById（id）将返回null。也请尝试更改此行：

fragment_two.populateDirectory(directory, this);

到此：

fragment_two.populateDirectory(directory, dual_fragments.this);

如果出于某种原因，某项活动以外的其他内容会被传递，那么它将会破坏。我知道你需要在OnClickListener中为一个按钮进行调用时有这样的区别，但我不熟悉你正在使用的监听器，所以我不确定是否有必要。而Matthew带来了一个好点，确保你指向正确的.xml文件。

相关问题
最新问题