public class MainActivity extends Activity Implements ICallInterface {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public void onTaskCompleted(Boolean result) {
if (result) {
Log.d(TAG, "1111111111111 11111111111 True condition ");
} else {
Log.d(TAG, "22222222222222222222 False condition ");
}
}
public interface ICallInterface {
void onTaskCompleted(Boolean result);
}
public class AsycData extends AsyncTask<String, Void, Void> {
ICallInterface mCallInterface;
// AsyncTask Data
// AsyncTask onPost
@Override
protected void onPostExecute(Void result) {
// call interface, set true value & call first activity.
mCallInterface.onTaskCompleted(true);
}
}
调用时出现空指针异常。
我知道我的 AsycData 声明出了问题,但找不到答案。
任何可以帮助我的人。
最佳答案
我已经修改了您的代码,现在它可以工作并在日志中打印真实值。现在你想做的事情都可以用代码来做。如果这对您有用,请放弃投票。
public class MainActivity extends Activity implements ICallInterface {
SecondClass second;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// second.execute();
second = new SecondClass(this);
second.execute();
}
/*
*
* @Override public void onTaskCompleted(Boolean result) { // TODO
* Auto-generated method stub if (result) {
* Log.d("tag","1111111111111 11111111111 True condition ");
* System.out.println(result); // System.out.println(str);
* Toast.makeText(getApplicationContext(), " "+result,
* Toast.LENGTH_LONG).show();
*
*
* } else { Log.d("tag","22222222222222222222 False condition "); }
*
* }
*/
@Override
public void onTaskCompleted(String result) {
// TODO Auto-generated method stub
System.out.println(result);
// System.out.println(str);
Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG)
.show();
}
}
public class SecondClass extends AsyncTask<String, String, String> {
ICallInterface mCallInterface;
public SecondClass(ICallInterface mcaCallInterface) {
// TODO Auto-generated constructor stub
this.mCallInterface = mcaCallInterface;
}
@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
String str = "Hello";
return str;
}
@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
mCallInterface.onTaskCompleted(result);
super.onPostExecute(result);
}
}
public interface ICallInterface {
void onTaskCompleted(String result);
}
关于java - 来自另一个类的 Android Interface 类显示空指针异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17377742/