Android 在一个应用中怎么启动另外一个已安装的应用

Android 在一个应用中如何启动另外一个已安装的应用

在自己的apk中如何来启动另外的一个apk

package com.cn;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {
	private Button myBut;
	private String tongfang = "com.android.tongfang";

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		myBut = (Button) findViewById(R.id.my_but);
		myBut.setOnClickListener(new Button.OnClickListener() {
			public void onClick(View v) {
				//Intent intent = new Intent(tongfang);
				//startActivity(intent);
			Intent mIntent = new Intent( ); 
				ComponentName comp = new ComponentName(tongfang, "com.android.tongfang.MainActivity");     
				mIntent.setComponent(comp); 
				mIntent.setAction("android.intent.action.VIEW"); 
				startActivity(mIntent);
			}
		});
	}
}