Intent之学习二（Activity间数据的传递）

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Activity的启动常常有两种方式：startActivity()与startActivityForResult()。接下来，就以这两种方式为例讲解使用Intent在Activity间进行数据的传递。

1、startActivity()
2、startActivityForResult()

1、startActivity()

用到的函数：startActivity(Intent intent)

从FirstActivity点击button1启动SecondActivity，在SecondActivity使用Log方式查看Intent传递的数据。

代码段

FirstActivity.class

Button button1 = (Button)findViewById(R.id.button1);        button1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(FirstActivity.this, SecondActivity.class);                int data = 1;                intent.putExtra("ExtraData",data);                startActivity(intent);            }        });

SecondActivity.class

Intent intent = getIntent();int data = intent.getIntExtra("ExtraData",-1);Log.d("SecondActivity",Integer.toString(data));

2、startActivityForResult()

用到的函数：
startActivityForResult(Intent intent, int requestCode)
setResult(int resultCode,Intent intent)
onActivityResult(int requestCode,int resultCode,Intent data)

从FirstActivity点击button1启动SecondActivity，并将Intent附带数据传给SecondActivity，在SecondActivity使用Log方式查看传递的数据。
从FirstActivity点击button3启动ThirdActivity,此处Intent没有附带数据。
分别从SecondActivity与ThirdActivity点击返回按键回到FirstActivity，并将Intent附带数据用Log方式打印出来。

代码段

FirstActivity.class

Button button1 = (Button)findViewById(R.id.button1);        button1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(FirstActivity.this, SecondActivity.class);                int data = 1;                intent.putExtra("ExtraData", data);                startActivityForResult(intent,2);            }        });

//隐式intent启动activity3        Button button3 = (Button)findViewById(R.id.button3);        button3.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent("com.example.test.ACTION_START");                intent.addCategory("com.example.test.MY_CATEGORY");                startActivityForResult(intent, 3);            }        });

@Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        switch (requestCode){            case 2:                if (resultCode==RESULT_OK){                    String return_data = data.getStringExtra("return");                    Log.d("FirstActivity",return_data);                }            case 3:                if (resultCode==RESULT_OK){                    String return_data = data.getStringExtra("return");                    Log.d("FirstActivity",return_data);                }        }    }

SecondActivity.class

Intent intent = getIntent();        int data = intent.getIntExtra("ExtraData",-1);        Log.d("SecondActivity", Integer.toString(data));

@Override    public void onBackPressed() {        Intent intent = new Intent();        intent.putExtra("return","Second_to_First");        setResult(RESULT_OK,intent);        finish();    }

ThirdActivity.class

@Override    public void onBackPressed() {        Intent intent = new Intent();        intent.putExtra("return", "Third_to_First");        setResult(RESULT_OK, intent);        finish();    }

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