如何修復無法解析方法“findViewById”

Question

我正在使用片段構建一個無線電流媒體應用程序，但我遇到了問題：

b_play = (Button) findViewById(R.id.b_play);

我已經嘗試過“在‘RadioFragment’中為‘findViewById’創建方法

b_play = (Button) findViewById(R.id.b_play);
b_play.setEnabled(false);
b_play.setText("LOADING");
mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
new PlayerTask().execute(stream);

該應用程序因錯誤而無法運行，我想修復該問題。

Answer 1

將您的視圖添加到此行

b_play = (Button) view.findViewById(R.id.b_play);

Answer 2

您必須在RadioFragment的view實例上調用findViewById 。

public class RadioFragment extends Fragment {

    Button b_play;
    MediaPlayer mediaPlayer;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_radio, container, false);

        b_play = (Button) view.findViewById(R.id.b_play);
        b_play.setEnabled(false);
        b_play.setText("LOADING");
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        new PlayerTask().execute(stream);

        return view;
    }
}

更新：根據作者的代碼。

public class RadioFragment extends Fragment {

    Button b_play;

    MediaPlayer mediaPlayer;

    boolean prepared = false;

    boolean started = false;

    String stream = "http://streaming.radiodifusao.org:8110/stream?type=.mp3";

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_radio, container, false);

        b_play = (Button) view.findViewById(R.id.b_play);
        b_play.setEnabled(false);
        b_play.setText("LOADING");

        b_play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (started) {
                    started = false;
                    mediaPlayer.pause();
                    b_play.setText("PLAY");

                } else {
                    started = true;
                    mediaPlayer.start();
                    b_play.setText("PAUSE");

                }
            }
        });

        mediaPlayer = new MediaPlayer();
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);

        new PlayerTask().execute(stream);

        return view;

    }

    class PlayerTask extends AsyncTask<String, Void, Boolean> {
        @Override
        protected Boolean doInBackground(String... strings) {

            try {
                mediaPlayer.setDataSource(strings[0]);
                mediaPlayer.prepare();
                prepared = true;
            } catch (IOException e) {
                e.printStackTrace();
            }

            return prepared;
        }

        @Override
        protected void onPostExecute(Boolean aBoolean) {
            super.onPostExecute(aBoolean);
            b_play.setEnabled(true);
            b_play.setText("PLAY");
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        if (started) {
            mediaPlayer.pause();
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        if (started) {
            mediaPlayer.start();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        if (prepared) {
            mediaPlayer.release();
        }
    }
}