startActivityForResult详解

爱被打了一巴掌 2024-04-18 19:58 30阅读 0赞

众所周知,startActivity是进行Activity之间的跳转,然后我在书上看到还有一个方法startActivityForResult.看了书上的解释,感觉不是很理解,于是自己试了这个方法.

`Activity1.java`

mBtn1.setOnClickListener(new View.OnClickListener() { 
                @Override
                public void onClick(View view) { 
                    //设置跳转Activity2的requestCode=1
                    startActivityForResult(new Intent(Activity1.this, Activity2.class), 1);
                }
            });
     mBtn2.setOnClickListener(new View.OnClickListener() { 
                @Override
                public void onClick(View view) { 
                    //设置跳转Activity3的requestCode=2
                    startActivityForResult(new Intent(Activity1.this, Activity3.class), 2);
                }
            });
    
    @Override
        protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) { 
            Log.i("selenium", "reqeustCode:" + requestCode);
            Log.i("selenium", "resultCode:" + resultCode);
        }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1NDUzMjY2_size_16_color_FFFFFF_t_70][]  
`Activity2.java`

@Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_2);
            setResult(200);
        }

![在这里插入图片描述][20190911135903912.png]  
`Activity3.java`

@Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_3);
            setResult(300);
        }

![在这里插入图片描述][20190911135947628.png]

首先我们在Activity1中新建了两个按钮,通过startActivityForResult分别跳转到了Activity2和Activity3,且requestCode分别为1和2.并且重写了`onActivityResult`方法(后面讲这个方法)

然后分别在Activity2和Activity3中设置了`setResult(200)`,`setResult(300)`,将resultCode分别设置为200和300.

运行程序,点击按钮跳转Activity2,再点击返回,发现在`onActicityResult`中定义的日志打印出来了,再,点击按钮跳转Activity3,再点击返回,发现在`onActicityResult`中定义的日志又打印出来了

![在这里插入图片描述][20190911141043334.png]  
由此我们可以知道,startActivityForResult与startActivity不同点在于,startActivity跳转后就跟原来Activity没什么关系了,原来的Activity不知道在跳转后的Activity中做了什么,做成功了吗,而startActivityForResult能够回调原来Activity中的`onActivityResult`方法.并且通过`requestCode`和`setResult(resultCode)`,我们能够区分是跳转到了哪个Activity,从哪个Activity返回的.

而`onActivityResult`回调函数被调用的时机是在你通过`startActivityForResult`进行跳转后点击返回或者调用`finish()`

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1NDUzMjY2_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/2622462fa18b408385056e981856e095.png
[20190911135903912.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/a14e3c9354d94b6eb07c84707cd96e8b.png
[20190911135947628.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/b678fbf232084cbb904e08a31857d3a7.png
[20190911141043334.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/9aa6c12bbce74ec89087218f4183608b.png