意图未定义尝试了很多，没有任何作用

Question

I get error with Intent. It says: intent is undefined . I've been searching a lot of other posts and it still doesn't work. Any ideas?

for your knowledge, i develop my own app with the basic of android developpes. Because my own intent didn't work, i used and created the exact same class as in the example, class DisplayMessageActivity but the problem remains the same, Here some of my code.

public class Main extends ActionBarActivity {

public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();


    }
    }
    catch(Exception e){
          System.out.println("fout zit hier");
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        return rootView;
    }
    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }
     }
} 

Answer 1

Try replacing the first parameter on the Intent constructor.

Intent intent = new Intent(this, DisplayMessageActivity.class); // wrong
Intent intent = new Intent(getActivity(), DisplayMessageActivity.class); // right

The first parameter is a Context object, and remember that a Fragment does not inherit from Context , so the solution is getting the one from the parent Activity.