我正在使用该项目https://github.com/googlesamples/android-RecyclerView作为参考来了解RecyclerView,并在这里实现MLProgrammer-Cim的答案来处理onClick事件。
在我的CustomAdapter
活动中,我试图启动speakNow();
另一个活动中的方法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);
}
....
}
这将返回一个NullPointerException以及MainActivity.speakNow(MainActivity.java:478)
其中的startActivityForResult(a, checka);
Adapter $ ViewHolder.onClick(CustomAdapter.java:287)ma.speakNow();
我已经阅读了各种“其他活动返回NPE的调用方法”,问题和答案,但不太确定这些方法如何适用于我的情况,因为MainActivity扩展SampleActivityBase
了公共的抽象类,它扩展了FragmentActivity。
我需要在哪里/如何初始化MainActivity ma = new MainActivity(); 所以它不为空吗?谢谢
例外情况是在startActivityForResult中引发的,这是因为您创建MainActivity ma = new MainActivity();
的活动与系统创建的活动不同,您创建的活动中没有任何内容,无法读取Activity
要执行的源代码startActivityForResult
,它取决于某些成员变量。因此您得到了nullpoint异常。您可以在适配器中添加设置器,将Activity的引用传递给适配器
public void setActivity(Activity aty) {
this.aty = aty;
}
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