2021-12-01 android 中activity的三种i

一、从一个Activity启动另一个Activity

1．建立Activity

public class IntentOneDemoActivity extends Activity {

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

}

public class IntentTwoDemoActivity extends Activity{

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

}

2.从IntentOneDemoActivity 启动IntentTwoDemoActivity

    Intent it=new Intent(IntentOneDemoActivity.this,IntentTwoDemoActivity.class);
                IntentOneDemoActivity.this.startActivity(it);

从IntentTwoDemoActivity 返回IntentOneDemoActivity

IntentTwoDemoActivity.this.finish();

二、从一个Activity传值到另一个Activity

1.设置值，启动IntentTwoDemoActivity

Intent it=new Intent(IntentOneDemoActivity.this,IntentTwoDemoActivity.class);
                it.putExtra("username", "zhangsan");
                IntentOneDemoActivity.this.startActivity(it);

2.在IntentTwoDemoActivity中接受

Intent it=IntentTwoDemoActivity.this.getIntent();
                String name=it.getStringExtra("username");
                Toast.makeText(IntentTwoDemoActivity.this, name, Toast.LENGTH_SHORT).show();

三、 从IntentOneDemoActivity中接受IntentTwoDemoActivity的返回值**

1．启动IntentTwoDemoActivity

Intent it=new Intent(IntentOneDemoActivity.this,IntentTwoDemoActivity.class);
                //it.putExtra("username", "zhangsan");
                //IntentOneDemoActivity.this.startActivity(it);
                IntentOneDemoActivity.this.startActivityForResult(it, 1);

2．IntentTwoDemoActivity设置返回值

Intent retIt=IntentTwoDemoActivity.this.getIntent();
                retIt.putExtra("retMsg", "lisi");
    //一定要有这句，设置返回结果。            IntentTwoDemoActivity.this.setResult(Activity.RESULT_OK, retIt);
                IntentTwoDemoActivity.this.finish();

3．IntentOneDemoActivity中接受返回值

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (resultCode) {
        case Activity.RESULT_OK:
            String retMsg=data.getStringExtra("retMsg");
            Toast.makeText(IntentOneDemoActivity.this, retMsg, Toast.LENGTH_SHORT).show();
            break;

        default:
            break;
        }
        super.onActivityResult(requestCode, resultCode, data);
    }