我花了很多时间寻找解决方案并需要帮助。
我的 Android 应用程序 Activity 中有一个嵌套的 AsyncTask,我希望允许用户在处理过程中旋转他的手机,而无需启动新的 AsyncTask。我尝试使用 onRetainNonConfigurationInstance() 和 getLastNonConfigurationInstance()。
我能够保留任务;但是,在旋转之后,它不会将 onPostExecute() 的结果保存到外部类变量中。当然,我尝试过 getter 和 setter。当我在 onPostExecute 中转储变量时,就可以了。但是当我尝试从 onClick 侦听器访问变量时,它为空。
也许代码会让你清楚问题。
public class MainActivity extends BaseActivity {
private String possibleResults = null;
private Object task = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.task = getLastNonConfigurationInstance();
setContentView(R.layout.menu);
if ((savedInstanceState != null)
&& (savedInstanceState.containsKey("possibleResults"))) {
this.possibleResults = savedInstanceState
.getString("possibleResults");
}
if (this.possibleResults == null) {
if (this.task != null) {
if (this.task instanceof PossibleResultWebService) {
((PossibleResultWebService) this.task).attach();
}
} else {
this.task = new PossibleResultWebService();
((PossibleResultWebService) this.task).execute(this.matchToken);
}
}
Button button;
button = (Button) findViewById(R.id.menu_resultButton);
button.setOnClickListener(resultListener);
}
@Override
protected void onResume() {
super.onResume();
}
OnClickListener resultListener = new OnClickListener() {
@Override
public void onClick(View v) {
Spinner s = (Spinner) findViewById(R.id.menu_heatSpinner);
int heatNo = s.getSelectedItemPosition() + 1;
Intent myIntent = new Intent(MainActivity.this,
ResultActivity.class);
myIntent.putExtra("matchToken", MainActivity.this.matchToken);
myIntent.putExtra("heatNo", String.valueOf(heatNo));
myIntent.putExtra("possibleResults",
MainActivity.this.possibleResults);
MainActivity.this.startActivityForResult(myIntent, ADD_RESULT);
}
};
private class PossibleResultWebService extends AsyncTask<String, Integer, Integer> {
private ProgressDialog pd;
private InputStream is;
private boolean finished = false;
private String possibleResults = null;
public boolean isFinished() {
return finished;
}
public String getPossibleResults() {
return possibleResults;
}
@Override
protected Integer doInBackground(String... params) {
// quite long code
}
public void attach() {
if (this.finished == false) {
pd = ProgressDialog.show(MainActivity.this, "Please wait...",
"Loading data...", true, false);
}
}
public void detach() {
pd.dismiss();
}
@Override
protected void onPreExecute() {
pd = ProgressDialog.show(MainActivity.this, "Please wait...",
"Loading data...", true, false);
}
@Override
protected void onPostExecute(Integer result) {
possibleResults = convertStreamToString(is);
MainActivity.this.possibleResults = possibleResults;
pd.dismiss();
this.finished = true;
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if (this.possibleResults != null) {
outState.putString("possibleResults", this.possibleResults);
}
}
@Override
public Object onRetainNonConfigurationInstance() {
if (this.task instanceof PossibleResultWebService) {
((PossibleResultWebService) this.task).detach();
}
return (this.task);
}
}