error on creating new intent

问题:

what's wrong with MainActivity.this here:

Intent myIntent = new Intent(MainActivity.this, SecondActivity.class);

when I press Ctrl+Space it suggest MainActivity.this but then rais an error :

this is Java :

    package com.example.explicitintent;

import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;

public class MainActivity extends ActionBarActivity {

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

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

    @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);
            Button btn = (Button)rootView.findViewById(R.id.button1);
            btn.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {
                    Intent myIntent = new Intent(MainActivity.this, SecondActivity.class);
                    startActivity(myIntent);


                }
            });
            return rootView;
        }
    }

}

and this is error:

回答1:

Try this..

If you use that intent in extends Activity your method is correct but your extends Fragment try below use getActivity()

Intent myIntent = new Intent(getActivity(), SecondActivity.class);
startActivity(myIntent);