在我的代码中,当服务器没有响应时,日志中会显示错误消息,但Toast
catch 块中的消息不会显示。我也试过getApplicationContext()
但没有帮助。当服务器没有响应时,我会强制关闭并显示消息“应用程序已意外停止。请稍后再试。”
package de.vogella.android.asyntask;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
public class ReadWebpageAsynTask extends Activity {
private static final String LOG_TAG = null;
private TextView textView;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textView = (TextView) findViewById(R.id.TextView01);
}
private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... urls) {
String response = "";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
InputStream content = execute.getEntity().getContent();
BufferedReader buffer = new BufferedReader(
new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
Toast.makeText(ReadWebpageAsynTask.this, "error server not responding
" + e.getMessage().toString(), Toast.LENGTH_LONG).show();
Log.e(LOG_TAG, "Connection Error ", e);
e.printStackTrace();
}
}
return response;
}
@Override
protected void onPostExecute(String result) {
textView.setText(result);
}
}
public void readWebpage(View view) {
DownloadWebPageTask task = new DownloadWebPageTask();
task.execute(new String[] { "http://www.vogella.de" });
}
}
这是logcat的输出
08-12 03:11:28.856: W/dalvikvm(824): threadid=7: thread exiting with uncaught
exception (group=0x4001d800)
08-12 03:11:28.876: E/AndroidRuntime(824): FATAL EXCEPTION: AsyncTask #1
08-12 03:11:28.876: E/AndroidRuntime(824): java.lang.RuntimeException: An error
occured while executing doInBackground()
08-12 03:11:28.876: E/AndroidRuntime(824): at
android.os.AsyncTask$3.done(AsyncTask.java:200)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.FutureTask.setException(FutureTask.java:124)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.FutureTask.run(FutureTask.java:137)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.lang.Thread.run(Thread.java:1096)
08-12 03:11:28.876: E/AndroidRuntime(824): Caused by: java.lang.RuntimeException:
Can't create handler inside thread that has not called Looper.prepare()
08-12 03:11:28.876: E/AndroidRuntime(824): at android.os.Handler.<init>
(Handler.java:121)
08-12 03:11:28.876: E/AndroidRuntime(824): at android.widget.Toast.<init>
(Toast.java:68)
08-12 03:11:28.876: E/AndroidRuntime(824): at
android.widget.Toast.makeText(Toast.java:231)
08-12 03:11:28.876: E/AndroidRuntime(824): at
08-12 03:11:28.876: E/AndroidRuntime(824): at
android.os.AsyncTask$2.call(AsyncTask.java:185)
08-12 03:11:28.876: E/AndroidRuntime(824): at
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
08-12 03:11:28.876: E/AndroidRuntime(824): ... 4 more