使用RecyclerView的Android語音識別

Question

我正在使用該項目https://github.com/googlesamples/android-RecyclerView作為參考來了解RecyclerView，並在這里實現MLProgrammer-Cim的答案來處理onClick事件。

在我的CustomAdapter活動中，我試圖啟動一個方法speakNow(); 在另一個活動MainActivity

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
private static final String TAG = "CustomAdapter";
...

public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    ...
    public MyViewHolderClicks mListener;
    private Context context;
    MainActivity ma = new MainActivity();

//        FragmentTransaction ft =     ((FragmentActivity)context).getSupportFragmentManager().beginTransaction();
//        SampleActivityBase fragment = (SampleActivityBase)ft.findFragmentByTag("SampleActivityBase");


    public ViewHolder(View myv, MyViewHolderClicks listener) {

        super(myv);
        mListener = listener;
        ....
        imageIcon.setOnClickListener(this);
        myv.setOnClickListener(this);
        this.context =context;


    }
    @Override
    public void onClick(View v) {
       int position = getLayoutPosition();
        if (v instanceof Button){
            mListener.onTomato((Button) v, getLayoutPosition());
            switch (v.getId()) {

               case R.id.button_for_cardview:
                   ma.speakNow();
 .....
 }
}

我的MainActivity

public class MainActivity extends SampleActivityBase {
....
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
     ....
    //Intent intent = new Intent(getApplicationContext(),     CustomAdapter.class);
    //startActivityForResult(new Intent(this, CustomAdapter.class), checka);
    if (savedInstanceState == null) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        RecyclerViewFragment fragment = new RecyclerViewFragment();
        transaction.replace(R.id.sample_content_fragment, fragment);
        transaction.commit();
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

  if (requestCode == checka && resultCode == RESULT_OK){
        ArrayList<String> results = data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);
        lv.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, results));

       .....
        }

    }
    super.onActivityResult(requestCode, resultCode, data);


}

protected void speakNow() {
    Intent a = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    a.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
    a.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 6);
    a.putExtra(RecognizerIntent.EXTRA_PROMPT, GlobalVariables.getInstance().getRightAnswer1());
    startActivityForResult(a, checka);
}
....

}

這會在MainActivity.speakNow(MainActivity.java:478)返回一個NullPointerException，它是startActivityForResult(a, checka); 和Adapter $ ViewHolder.onClick（CustomAdapter.java:287），它是ma.speakNow();

我已經閱讀了各種“其他活動返回NPE的調用方法”，問題和答案，但不太確定這些方法如何適用於我的案例，因為MainActivity擴展了SampleActivityBase ， SampleActivityBase是擴展FragmentActivity的公共抽象類。

我需要在哪里/如何初始化MainActivity ma = new MainActivity（）; 所以它不為空嗎？ 謝謝

Answer 1

在startActivityForResult中引發該異常，這是因為MainActivity ma = new MainActivity();創建的Activity MainActivity ma = new MainActivity(); 與系統創建的Activity不同，您創建的Activity中沒有任何內容，請讀取Activity的源代碼以執行startActivityForResult ，這取決於某些成員變量。因此，您會得到nullpoint異常。 您可以在適配器中添加設置器，將Activity的引用傳遞給適配器

public void setActivity(Activity aty) {
    this.aty = aty;
}