MainActivity不包含类

Question

如何解决此问题？

MainActivity.this不是封闭类。

谢谢

public class uploadToServer extends AsyncTask<Void, Void, String> { 

protected void onPreExecute() { 
    super.onPreExecute(); 
    ProgressDialog pd= new ProgressDialog(MainActivity.this); //error is here 
    pd.setMessage("Wait image uploading!"); 
    pd.show(); 
} 
} 

Answer 1

在AsyncTask构造，通过Context &使用它，当你从MainActivity这样需要

public class uploadToServer extends AsyncTask<Void, Void, String> { 
    private Context mContext; 
    public uploadToServer (Context context){ 
     mContext = context; 
    } 

    protected void onPreExecute() { 
     super.onPreExecute(); 
     ProgressDialog pd= new ProgressDialog(mContext); //change is here 
     pd.setMessage("Wait image uploading!"); 
     pd.show(); 
    } 
} 

呼叫，

uploadToServer task = new uploadToServer(getApplicationContext()); 
task.execute();