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从自定义列表视图启动活动

2012-07-05 71 views
0

我试图从自定义lisview启动活动。我通过创建一个新的意图来唤醒onItemclick方法并调用这个类！从自定义列表视图启动活动

public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) { 

    if (position == 0) { 
     Intent i = new Intent(getApplicationContext(), InstalledApps.class); 
     startActivity(i); 
    } 
}

但是当我尝试启动它时，它给了我一个空指针异常。我想要做的是，获取点击项目的位置并通过if子句将其引导到正确的活动。以下是日志猫输出。

07-05 04:39:52.718: W/dalvikvm(3189): threadid=1: thread exiting with uncaught exception (group=0x40a13300) 
07-05 04:39:52.758: E/AndroidRuntime(3189): FATAL EXCEPTION: main 
07-05 04:39:52.758: E/AndroidRuntime(3189): java.lang.NullPointerException 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at com.sliit.droidman.thirdpartyapplist.ListViewAdapter.getView(ListViewAdapter.java:69) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.AbsListView.obtainView(AbsListView.java:2267) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1244) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.ListView.onMeasure(ListView.java:1156) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.View.measure(View.java:15172) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at  android.widget.LinearLayout.measureVertical(LinearLayout.java:681) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:574) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.View.measure(View.java:15172) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.View.measure(View.java:15172) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:833) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:574) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.View.measure(View.java:15172) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2148) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.View.measure(View.java:15172) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1848) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1100) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1273) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.Choreographer.doCallbacks(Choreographer.java:555) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.Choreographer.doFrame(Choreographer.java:525) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.os.Handler.handleCallback(Handler.java:615) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.os.Handler.dispatchMessage(Handler.java:92) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.os.Looper.loop(Looper.java:137) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at android.app.ActivityThread.main(ActivityThread.java:4745) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
07-05 04:39:52.758: E/AndroidRuntime(3189):  at dalvik.system.NativeStart.main(Native Method)

请让我知道我在做什么错在这里！

适配器类。

package com.sliit.droidman.thirdpartyapplist; 
import com.sliit.droidman.R; 

import android.app.Activity; 
import android.graphics.drawable.Drawable; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ImageView; 
import android.widget.TextView; 

public class ListViewAdapter extends BaseAdapter 
{ 
Activity context; 
String title[]; 
String description[]; 
Drawable icon[]; 

public ListViewAdapter(Activity context, String[] title, String[] description , Drawable[] ico) { 
    super(); 
    this.context = context; 
    this.title = title; 
    this.description = description; 
    this.icon = ico; 
} 

public int getCount() { 
    // TODO Auto-generated method stub 
    return title.length; 
} 

public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return null; 
} 

public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return 0; 
} 

private class ViewHolder { 
    TextView txtViewTitle; 
    TextView txtViewDescription; 
    ImageView image; 
} 

public View getView(int position, View convertView, ViewGroup parent) 
{ 
    // TODO Auto-generated method stub 
    ViewHolder holder; 
    LayoutInflater inflater = context.getLayoutInflater(); 

    if (convertView == null) 
    { 
     convertView = inflater.inflate(R.layout.listitem_row, null); 
     holder = new ViewHolder(); 
     holder.txtViewTitle = (TextView) convertView.findViewById(R.id.appname); 
     holder.txtViewDescription = (TextView) convertView.findViewById(R.id.packagename); 
     holder.image = (ImageView) convertView.findViewById(R.id.avatar); 
     convertView.setTag(holder); 
    } 
    else 
    { 
     holder = (ViewHolder) convertView.getTag(); 
    } 

    holder.txtViewTitle.setText(title[position]); 
    holder.txtViewDescription.setText(description[position]); 
    holder.image.setImageDrawable(icon[position]); 

return convertView; 
} 

}

来源

2012-07-05 Imesh Chandrasiri

+0

发布你的getView（ListViewAdapter.java:69）方法和类.. – 2012-07-05 20:08:22

+0

我加了！ nd我无法看到适配器类中有错误！ :( – 2012-07-05 20:22:12

+0

请指定具体例外的代码行，这会让问题变得更加清晰 – Egor 2012-07-05 20:56:45

回答

1

07-05 04:39:52.758: E/AndroidRuntime(3189): at com.sliit.droidman.thirdpartyapplist.ListViewAdapter.getView(ListViewAdapter.java:69)

你必须在com.sliit.droidman.thirdpartyapplist.ListViewAdapter的getView方法的69行空指针。找出导致空指针的原因并确保它不会发生。

看来，第69行是一个可能导致此以下

holder.txtViewTitle.setText(title[position]);

有些事情：

  • 也许标题数组为null。我认为如果只是说position的参数太大，你会得到一个ArrayIndexOutOfBoundsException。
  • 的holder实例的txtViewTitle成员是null，可能是因为ID R.id.appname是不正确线59

您可以通过将上线69断点在调试和检查的值算出这个holder.txtViewTitle和title。

来源

2012-07-05 20:08:30

+0

除了上面的答案，实际上这并不能回答用户的问题，您应该发表评论以尝试弄清楚这行代码究竟是什么，然后尝试帮助解决它。 – Egor 2012-07-05 20:55:52

0

试试这个：

package com.sliit.droidman.thirdpartyapplist; 
import com.sliit.droidman.R; 

import android.app.Activity; 
import android.graphics.drawable.Drawable; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ImageView; 
import android.widget.TextView; 

public class ListViewAdapter extends BaseAdapter 
{ 
Activity context; 
String title[]; 
String description[]; 
Drawable icon[]; 

public ListViewAdapter(Activity context, String[] title, String[] description , Drawable[] ico) { 
    super(); 
    this.context = context; 
    this.title = title; 
    this.description = description; 
    this.icon = ico; 
} 

public int getCount() { 
    // TODO Auto-generated method stub 
    return title.length; 
} 

public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return null; 
} 

public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return 0; 
} 

//You have to overide the getView method 
@Override 
public View getView(int position, View convertView, ViewGroup parent) 
{ 
    //added row, to convert view 
    View row = convertView; 
    ViewHolder holder; 


    if (convertView == null) 
    { 
     //added casting to the context 
     LayoutInflater inflater = ((Activity)this.context).getLayoutInflater();  
     //made changes here 
     row = inflater.inflate(R.layout.listitem_row, parent, false); 
     holder = new ViewHolder(); 
     holder.txtViewTitle = (TextView) convertView.findViewById(R.id.appname); 
     holder.txtViewDescription = (TextView) convertView.findViewById(R.id.packagename); 
     holder.image = (ImageView) convertView.findViewById(R.id.avatar); 
     row.setTag(holder); 
    } 
    else 
    { //added row 
     holder = (ViewHolder) row.getTag(); 
    } 

    holder.txtViewTitle.setText(title[position]); 
    holder.txtViewDescription.setText(description[position]); 
    holder.image.setImageDrawable(icon[position]); 
//changed to row 
return row; 
} 

} 
static class ViewHolder { 
    TextView txtViewTitle; 
    TextView txtViewDescription; 
    ImageView image; 
}

基本上，我创建的类的listadapter之外的静态ViewHolder类，并提出了其他的一些小的改动，包括重写你的getView方法。我在评论中发表了改变。让我知道这个是否奏效！希望这可以帮助！

来源

2012-07-05 21:45:46 BlackHatSamurai

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