Android 使用 RecyclerView 进行语音识别

Question

我正在使用这个项目 https://github.com/googlesamples/android-RecyclerView as reference to learn about RecyclerView, and implementing the answer by MLProgrammer-Cim here 来处理 onClick 事件。

在我的 CustomAdapteractivity 中，我正在尝试启动另一个 activity MainActivity

中的方法 speakNow();

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);
}
....

}

这 return 中的一个 NullPointerException MainActivity.speakNow(MainActivity.java:478) 这是这个 startActivityForResult(a, checka); 和 Adapter$ViewHolder.onClick(CustomAdapter.java:287) 即 ma.speakNow();

我已经阅读了各种 "calling Methods from other activities returning NPE"、问题和答案，不太确定这些如何适用于我的案例，因为 MainActivity 扩展了 SampleActivityBase，这是一个 public 抽象 class 它扩展了 FragmentActivity.

我需要在哪里/如何初始化 MainActivity ma = new MainActivity();所以它不为空？谢谢

Answer 1

在startActivityForResult中抛出异常，那是因为MainActivity ma = new MainActivity();创建的Activity与系统创建的Activity不同，Activity你创建的里面什么都没有，看Activity的源代码执行startActivityForResult，这取决于你的某个成员variable.so你得到了空点异常。您可以在适配器中添加一个 setter，将 Activity 的引用传递给适配器

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

Android 使用 RecyclerView 进行语音识别

Android Speech Recognition with RecyclerView

android

methods

custom-adapter

android-recyclerview