我使用broadcastReceiver接收wifi信号强度，并且我试图在progressBar中显示wifi级别。但是我得到了一个例外。
private class MonAdaptateurDeListe extends ArrayAdapter<ScanResult> {
public MonAdaptateurDeListe(){
super(MainActivity.this,R.layout.item_layout,results);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View itemView = convertView;
if (itemView == null){
itemView = getLayoutInflater().inflate(R.layout.item_layout, parent, false);
}
progressBar = (ProgressBar) findViewById(R.id.progressBar1);
ImageView imageView = (ImageView)itemView.findViewById(R.id.imageView1);
imageView.setImageResource(R.drawable.network);
Log.i("position",position+"");
Log.i("position",results+"");
if (results != null)
{
progressBar.setMax(-100);
progressBar.setMax(-20);
progressBar.setProgress(results.get(position).level);
}
return itemView;
}
}
这是我的XML文件：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/security"
android:layout_alignParentRight="true"
android:layout_marginRight="16dp"
android:minWidth="70dp"
android:progressDrawable="@drawable/greenprogress" />
这就是我得到的LogCat，它指向＆＃34; progressBar.setMax（-100）;＆＃34; line：
05-12 11:24:59.156: E/AndroidRuntime(5375): FATAL EXCEPTION: main
05-12 11:24:59.156: E/AndroidRuntime(5375): java.lang.NullPointerException
05-12 11:24:59.156: E/AndroidRuntime(5375): at com.example.listwifi.MainActivity$MonAdaptateurDeListe.getView(MainActivity.java:146)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.AbsListView.obtainView(AbsListView.java:2207)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.ListView.onMeasure(ListView.java:1162)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.View.measure(View.java:15635)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.RelativeLayout.measureChild(RelativeLayout.java:666)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:477)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.View.measure(View.java:15635)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4919)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.View.measure(View.java:15635)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.LinearLayout.measureVertical(LinearLayout.java:850)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.View.measure(View.java:15635)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4919)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-12 11:24:59.156: E/AndroidRuntime(5375): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2200)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.View.measure(View.java:15635)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2165)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1249)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1443)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1139)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4872)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.Choreographer.doCallbacks(Choreographer.java:579)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.Choreographer.doFrame(Choreographer.java:548)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.os.Handler.handleCallback(Handler.java:800)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.os.Handler.dispatchMessage(Handler.java:100)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.os.Looper.loop(Looper.java:194)
05-12 11:24:59.156: E/AndroidRuntime(5375): at android.app.ActivityThread.main(ActivityThread.java:5371)
05-12 11:24:59.156: E/AndroidRuntime(5375): at java.lang.reflect.Method.invokeNative(Native Method)
05-12 11:24:59.156: E/AndroidRuntime(5375): at java.lang.reflect.Method.invoke(Method.java:525)
05-12 11:24:59.156: E/AndroidRuntime(5375): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
05-12 11:24:59.156: E/AndroidRuntime(5375): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
05-12 11:24:59.156: E/AndroidRuntime(5375): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
您是否将进度条设置为 -100 ？那不是你的错吗？我非常确定进度条的最低允许值是...... 0.请参阅the ProgressBar API documentation，您甚至无法为进度条设置最小值（但您可以设置最大值） ）。
答案 1 :(得分：0)
我找到了一个解决方案。希望它会帮助别人。
private Handler mHandler = new Handler();
private ProgressBar progressBar;
if (results != null)
{
pos = position;
// Start lengthy operation in a background thread
new Thread(new Runnable() {
public void run() {
// Update the progress bar
mHandler.post(new Runnable() {
public void run() {
progressBar.setProgress(30);
}
});
}
}
}).start();