我有一个应用程序，它读取外部数据库并提取结果以填充ListView，其行包含TextView和Button。但是当我将普通Button更改为ImageButton时，应用会在启动后立即停止。我的每行.xml如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/listButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:layout_marginRight="41dp"
android:layout_marginTop="16dp"
android:background="@null"
android:src="@drawable/ciplus" />
<TextView
android:id="@+id/listText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/listButton"
android:layout_marginRight="56dp"
android:layout_toLeftOf="@+id/listButton"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
</RelativeLayout>
在ImageButton标记旁边，我还会收到一条警告：图片上显示[Accessibility] Missing contentDescription属性。我不确定它是不是原因。
如果只是Button，该程序运行正常。我不知道为什么将其更改为ImageButton会导致问题。提前谢谢。
这里是java代码：
public class MainActivity extends Activity {
static final private String LOG_TAG = "main";
private ArrayList<Content> aList;
private class Content{
Content() {};
public String title;
public String url;
}
private class MyAdapter extends ArrayAdapter<Content>{
int resource;
public MyAdapter(Context _context, int _resource, List<Content> titles) {
super(_context, _resource, titles);
resource = _resource;
// this.context = _context;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LinearLayout newView;
final Content content = getItem(position);
// Inflate a new view if necessary.
if (convertView == null) {
newView = new LinearLayout(getContext());
String inflater = Context.LAYOUT_INFLATER_SERVICE;
LayoutInflater vi = (LayoutInflater) getContext().getSystemService(inflater);
vi.inflate(resource, newView, true);
} else {
newView = (LinearLayout) convertView;
}
// Fills in the view.
TextView tv = (TextView) newView.findViewById(R.id.listText);
Button b = (Button) newView.findViewById(R.id.listButton);
tv.setText(content.title);
// Sets a listener for the button, and a tag for the button as well.
b.setTag(Integer.toString(position));
b.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Reacts to a button press.
Intent intent = new Intent(MainActivity.this, WebPage.class);
Bundle bundle = new Bundle();
bundle.putString("URL", content.url);
intent.putExtras(bundle);
startActivity(intent);
}
});
return newView;
}
}
class MyAsyncTask extends AsyncTask<String, String, String> {
private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
InputStream inputStream = null;
String result = "";
Content content;
protected void onPreExecute() {
super.onPreExecute();
progressDialog.setMessage("Downloading the news...");
progressDialog.show();
progressDialog.setOnCancelListener(new OnCancelListener() {
public void onCancel(DialogInterface arg0) {
MyAsyncTask.this.cancel(true);
}
});
}
@Override
protected String doInBackground(String... params) {
String url_select = params[0];
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
try {
// Set up HTTP post
// HttpClient is more then less deprecated. Need to change to URLConnection
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url_select);
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// Read content & Log
inputStream = httpEntity.getContent();
} catch (UnsupportedEncodingException e1) {
Log.e("UnsupportedEncodingException", e1.toString());
e1.printStackTrace();
} catch (ClientProtocolException e2) {
Log.e("ClientProtocolException", e2.toString());
e2.printStackTrace();
} catch (IllegalStateException e3) {
Log.e("IllegalStateException", e3.toString());
e3.printStackTrace();
} catch (IOException e4) {
Log.e("IOException", e4.toString());
e4.printStackTrace();
}
// Convert response to string using String Builder
try {
BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"), 8);
StringBuilder sBuilder = new StringBuilder();
String line = null;
while ((line = bReader.readLine()) != null) {
sBuilder.append(line + "\n");
}
inputStream.close();
result = sBuilder.toString();
} catch (Exception e) {
Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
}
return result;
} // protected Void doInBackground(String... params)
protected void onPostExecute(String result) {
//parse JSON data
try {
super.onPostExecute(result);
Log.i(LOG_TAG, result);
JSONObject object = new JSONObject(result);
JSONArray jArray = object.getJSONArray("sites");
for(int i=0; i < jArray.length(); i++) {
JSONObject jObject = jArray.getJSONObject(i);
content = new Content();
if (jObject.has("title") && jObject.has("url")){
content.title = jObject.getString("title");
content.url = jObject.getString("url");
aList.add(content);
aa.notifyDataSetChanged();
}
} // End Loop
progressDialog.dismiss();
} catch (JSONException e) {
// progressDialog.dismiss();
Log.e("JSONException", "Error: " + e.toString());
}
} // protected void onPostExecute(String result)
}
private MyAdapter aa;
private MyAsyncTask loadTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadTask = new MyAsyncTask();
loadTask.execute("http://luca-ucsc.appspot.com/jsonnews/default/news_sources.json");
aList = new ArrayList<Content>();
aa = new MyAdapter(this, R.layout.list_element, aList);
ListView myListView = (ListView) findViewById(R.id.listView1);
myListView.setAdapter(aa);
aa.notifyDataSetChanged();
}
public void refresh(View v){
if (loadTask.getStatus() == AsyncTask.Status.FINISHED){
aList.clear();
aa.notifyDataSetChanged();
new MyAsyncTask().execute("http://luca-ucsc.appspot.com/jsonnews/default/news_sources.json");
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
这里的logcat信息大致从午餐到停止：
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 3, Width = 6, current total allocated size out of MAX(1024) = 178
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 7, Width = 6, current total allocated size out of MAX(1024) = 186
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 2, current total allocated size out of MAX(1024) = 194
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 15, Width = 9, current total allocated size out of MAX(1024) = 198
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 8, Width = 7, current total allocated size out of MAX(1024) = 209
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 218
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 14, current total allocated size out of MAX(1024) = 231
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 8, Width = 8, current total allocated size out of MAX(1024) = 247
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 16, Width = 2, current total allocated size out of MAX(1024) = 257
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 0, Width = 0, current total allocated size out of MAX(1024) = 261
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 3, Width = 3, current total allocated size out of MAX(1024) = 263
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 13, current total allocated size out of MAX(1024) = 268
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 3, Width = 4, current total allocated size out of MAX(1024) = 283
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 14, current total allocated size out of MAX(1024) = 289
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 8, current total allocated size out of MAX(1024) = 305
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 4, Width = 3, current total allocated size out of MAX(1024) = 315
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 8, current total allocated size out of MAX(1024) = 320
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 2, Width = 7, current total allocated size out of MAX(1024) = 330
04-28 00:09:03.859: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 2, Width = 7, current total allocated size out of MAX(1024) = 339
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 6, Width = 8, current total allocated size out of MAX(1024) = 348
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 15, Width = 9, current total allocated size out of MAX(1024) = 358
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 7, current total allocated size out of MAX(1024) = 369
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 9, current total allocated size out of MAX(1024) = 378
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 7, Width = 7, current total allocated size out of MAX(1024) = 389
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 10, current total allocated size out of MAX(1024) = 398
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 9, current total allocated size out of MAX(1024) = 410
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 9, current total allocated size out of MAX(1024) = 421
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 3, current total allocated size out of MAX(1024) = 432
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 3, current total allocated size out of MAX(1024) = 437
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 3, Width = 5, current total allocated size out of MAX(1024) = 442
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 9, current total allocated size out of MAX(1024) = 449
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 10, Width = 5, current total allocated size out of MAX(1024) = 460
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 15, Width = 9, current total allocated size out of MAX(1024) = 467
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 10, Width = 14, current total allocated size out of MAX(1024) = 478
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 18, Width = 5, current total allocated size out of MAX(1024) = 494
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 18, Width = 5, current total allocated size out of MAX(1024) = 13
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 9, current total allocated size out of MAX(1024) = 494
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 2, Width = 9, current total allocated size out of MAX(1024) = 505
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 10, Width = 9, current total allocated size out of MAX(1024) = 516
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 9, current total allocated size out of MAX(1024) = 527
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 9, current total allocated size out of MAX(1024) = 538
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 8, current total allocated size out of MAX(1024) = 549
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 6, current total allocated size out of MAX(1024) = 559
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 10, Width = 14, current total allocated size out of MAX(1024) = 567
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 11, Width = 8, current total allocated size out of MAX(1024) = 583
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 9, current total allocated size out of MAX(1024) = 593
04-28 00:09:03.869: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 10, Width = 8, current total allocated size out of MAX(1024) = 604
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 3, current total allocated size out of MAX(1024) = 614
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 619
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 15, Width = 8, current total allocated size out of MAX(1024) = 632
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 9, Width = 8, current total allocated size out of MAX(1024) = 642
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 9, current total allocated size out of MAX(1024) = 652
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 9, current total allocated size out of MAX(1024) = 663
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 9, current total allocated size out of MAX(1024) = 674
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 685
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 18, Width = 4, current total allocated size out of MAX(1024) = 698
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 18, Width = 4, current total allocated size out of MAX(1024) = 20
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 698
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 16, current total allocated size out of MAX(1024) = 711
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 19, Width = 6, current total allocated size out of MAX(1024) = 729
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 19, Width = 6, current total allocated size out of MAX(1024) = 26
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 729
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 14, current total allocated size out of MAX(1024) = 742
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 758
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 11, current total allocated size out of MAX(1024) = 771
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 10, current total allocated size out of MAX(1024) = 784
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 15, Width = 12, current total allocated size out of MAX(1024) = 796
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 10, current total allocated size out of MAX(1024) = 810
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 11, current total allocated size out of MAX(1024) = 822
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 11, current total allocated size out of MAX(1024) = 835
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 14, Width = 10, current total allocated size out of MAX(1024) = 848
04-28 00:09:03.879: E/OpenGLRenderer(14018): HUAWEI_DEBUG: glyph's Height = 13, Width = 12, current total allocated size out of MAX(1024) = 860
04-28 00:09:03.919: I/ActivityManager(279): Displayed ucsc.luca.listviewexample/com.example.newsapp.MainActivity: +467ms
04-28 00:09:04.009: W/SignalStrength(356): getLTELevel - rsrp:2147483647 snr:2147483647 rsrpIconLevel:-1 snrIconLevel:-1
04-28 00:09:04.009: W/SignalStrength(356): getLTELevel - rssi:99 rssiIconLevel:0
04-28 00:09:04.009: W/SignalStrength(356): getGsmLevel=2
04-28 00:09:04.009: W/SignalStrength(356): getLevel=2
04-28 00:09:04.309: W/dalvikvm(14018): threadid=1: thread exiting with uncaught exception (group=0x40d06390)
04-28 00:09:04.849: E/Sensors(279): GsSensor: line +83 ~~~handle===0~~en==0~~!n
04-28 00:09:04.859: E/Sensors(279): GsSensor::setDelay: line +114 ~~~handle===0~~ns==200000000~~
04-28 00:09:04.879: I/WindowManager(279): SCREENLAYOUT_SIZE (1:small, 2:normal, 3:large, 4:xlarge) 2
04-28 00:09:04.879: I/fitatc(485): no preference set
04-28 00:09:04.929: E/OpenGLRenderer(485): HUAWEI_DEBUG: glyph's Height = 8, Width = 3, current total allocated size out of MAX(1024) = 0
04-28 00:09:04.929: E/OpenGLRenderer(485): HUAWEI_DEBUG: glyph's Height = 0, Width = 0, current total allocated size out of MAX(1024) = 5
04-28 00:09:04.929: E/OpenGLRenderer(485): HUAWEI_DEBUG: glyph's Height = 7, Width = 6, current total allocated size out of MAX(1024) = 7
04-28 00:09:04.929: E/OpenGLRenderer(485): HUAWEI_DEBUG: glyph's Height = 8, Width = 4, current total allocated size out of MAX(1024) = 15
04-28 00:09:04.929: E/OpenGLRenderer(485): HUAWEI_DEBUG: glyph's Height = 9, Width = 6, current total allocated size out of MAX(1024) = 21
04-28 00:09:06.009: W/SignalStrength(356): getLTELevel - rsrp:2147483647 snr:2147483647 rsrpIconLevel:-1 snrIconLevel:-1
04-28 00:09:06.009: W/SignalStrength(356): getLTELevel - rssi:99 rssiIconLevel:0
04-28 00:09:06.009: W/SignalStrength(356): getGsmLevel=2
04-28 00:09:06.009: W/SignalStrength(356): getLevel=2
04-28 00:09:06.229: W/SignalStrength(457): SignalStrength before validate=SignalStrength: 5 255 -1 -1 -1 -1 -1 99 -32767 -32767 -32767 -32767.0.0 cdma
04-28 00:09:06.229: W/SignalStrength(457): SignalStrength after validate=SignalStrength: 5 255 -120 -160 -120 -1 -1 99 2147483647 2147483647 2147483647 -32767.0.0 cdma
04-28 00:09:06.329: W/lights(279): TP Button Light current value is 60
04-28 00:09:06.329: W/lights(279): button_backlight:property_get,percent =0
04-28 00:09:06.359: W/MemoryDealer(147): madvise(0x42261000, 16384, MADV_REMOVE) returned Operation not supported on transport endpoint
答案 0 :(得分：2)
在xml布局中，您使用的是“ImageButton”，但在您的自定义“MyAdapter”中，您将其称为“按钮”。这就是为什么你可能会得到“ClassCastException”。
将Button b = (Button) newView.findViewById(R.id.listButton);更改为ImageButton b = (ImageButton) newView.findViewById(R.id.listButton);