在不同Java类文件的活动中制作祝酒词

Question

我有2个.java文件:AnswerActivity.java

public class AnswerActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_answer);

        new JSONTask().execute("https://example.com/api.php");
    }
}

和 JSONTask.java

public class JSONTask extends AsyncTask<String, String, String> {

    @Override
    protected String doInBackground(String... params) {

    //--- some code cut here ---//

    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);

        Intent i = new Intent(this, AnswerActivity.class);
        Toast.makeText(i, result, Toast.LENGTH_LONG).show();
    }
}

我的最后两行总是给我错误:

    Intent i = new Intent(this, AnswerActivity.class);
    Toast.makeText(i, result, Toast.LENGTH_LONG).show();

我想将其result作为Toa​​st 显示在AnswerActivity中.但为什么我总是收到此错误消息？

Error:(68, 20) error: no suitable constructor found for Intent(JSONTask,Class<AnswerActivity>)
constructor Intent.Intent(String,Uri) is not applicable
(argument mismatch; JSONTask cannot be converted to String)
constructor Intent.Intent(Context,Class<?>) is not applicable
(argument mismatch; JSONTask cannot be converted to Context)

Error:(69, 14) error: no suitable method found for makeText(Intent,String,int)
method Toast.makeText(Context,CharSequence,int) is not applicable
(argument mismatch; Intent cannot be converted to Context)
method Toast.makeText(Context,int,int) is not applicable
(argument mismatch; Intent cannot be converted to Context)

我在这里想念的是什么？谢谢

Answer 1

您需要一个上下文来显示Toast.通常它是Activity或Fragment具有上下文.但既然你AsyncTask不是你的内在阶级,AnswerActivity你就没有上下文的参考.所以你可以传递Activity构造函数并使用它

public class JSONTask extends AsyncTask<String, String, String> {

    private Context context;

    public JSONTask(Context context){
      this.context = context;
    }

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(context, result, Toast.LENGTH_LONG).show();
    }
}

并使用它

new JSONTask(this)... // and so on

这样做的最大好处是,你不会保留对它的引用Activity,只是传递Context- 因为Activity确实扩展了Context.