Android 启动另一个App/apk中的Activity实现代码

 public void OnStartActivityClicked(View view) {
  Intent intent = new Intent(Intent.ACTION_VIEW);

  String packageName = "com.lazytech.projecta";
  String className = "com.lazytech.projecta.MainActivity";
  intent.setClassName(packageName, className);

  //second method
//  intent.setComponent(new ComponentName(
//    "com.lazytech.projecta",
//    "com.lazytech.projecta.MainActivity"
//  ));
  Bundle bundle = new Bundle();
  bundle.putString("msg", "this message is from project B ");
  intent.putExtras(bundle);

  intent.putExtra("pid", android.os.Process.myPid());

  startActivityForResult(intent, 1);
//  startActivity(intent);
 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  switch (requestCode) {
   case 1:
    if(resultCode == RESULT_OK) {
     textView.setText(data.getStringExtra("result"));
    }
    break;
  }
 }

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textView = (TextView)findViewById(R.id.text);

  Intent intent = getIntent();
  if(intent != null) {
   textView.setText(intent.getStringExtra("msg"));
  }
 }

 public void OnSendResult(View view) {
  Intent intent = new Intent();
  intent.putExtra("result","OK! from project a.");
  this.setResult(RESULT_OK,intent);
  this.finish();
 }