Android学习——Intent传递数据

向下一个应用传递数据

 button1.setOnClickListener(new View.OnClickListener(){
     @Override
     public void onClick(View v) {
          String data = "你好呀，SecondActivity";
         Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
         intent.putExtra("extra_data",data);//第一个参数是键，第二个参数才是真正的数据
         startActivity(intent);
     }
 });

在SecondActivity重写的onCreate方法中，加入如下代码：

 @Override
 protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.second_layout);
     Intent intent = getIntent();//注意这里是getIntent()
     String data = intent.getStringExtra("extra_data");
     Log.d("SecondActivity",data);
//····
 }

返回数据给上一个活动

 button1.setOnClickListener(new View.OnClickListener(){
     @Override
     public void onClick(View v) {
         Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
         startActivityForResult(intent,1);
     }
 });

Button button2 = (Button)findViewById(R.id.button_2);
button2.setOnClickListener(new View.OnClickListener(){
    @Override
    public void onClick(View v) {
        Intent intent = new Intent();
        intent.putExtra("data_return","你好呀 FirstActivity");
        setResult(RESULT_OK,intent);
        finish();
    }
});

在FirstActivity中重写onActivityResult()方法来得到返回数据：

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch (requestCode){
        case 1:
            if(resultCode == RESULT_OK){
                String returnedData = data.getStringExtra("data_return");
                Log.d("FirstActivity",returnedData);
            }
            break;
            default:
    }
    super.onActivityResult(requestCode, resultCode, data);
}

如果用户不是通过点击button 2按钮返回到FirstActivity，而是通过按下手机的Back键回到FirstActivity，这个时候我们就要监听Back键来发送数据给上层应用了：

    @Override
    public void onBackPressed(){
        Intent intent = new Intent();
        intent.putExtra("data_return","你好呀，，，FirstActivity");
        setResult(RESULT_OK,intent);
        finish();
    }