android之startActivityForResult介绍

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startActivityForResult

startActivityForResult与startActivity类似都是用来跳转界面。

但是，startActivityForResult和startActivity也有不同的地方：

• startActivity仅仅是跳转到目标页面，若是想跳回当前页面，则必须再使用一次startActivity。
• startActivityForResult可以一次性完成这项任务，当程序执行到这段代码的时候，假若从T1Activity跳转到下一个Text2Activity，而当这个Text2Activity调用了finish()方法以后，程序会自动跳转回T1Activity，并调用前一个T1Activity中的onActivityResult方法。

也就是执行startActivityForResult后可以从打开的界面，再返回到主界面去。

相关的接口：

startActivityForResult(Intent intent, Int requestCode)
setResut(int resultCode, Intent intent)
onActivityResult(int requestCode, int resultCode, Intent intent)

实战代码

MainActivity.java：

package com.exmple.transition;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.switchButton);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d("test---", "onClick---111--");
                Intent intent =  new Intent();
                intent.setClass(MainActivity.this, test2.class);

                startActivityForResult(intent, 1);

                overridePendingTransition(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
//                overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
//                overridePendingTransition(0, 0);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        Log.d("test---", "resultCode="+resultCode);
    }
}

test2.java:

package com.exmple.transition;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class test2 extends AppCompatActivity {
    Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test2);

        button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d("test---", "onClick---222--");
                setResult(1);
                finish();
            }
        });
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/switchButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

activity_test2.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".test2">


    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="go home"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

执行效果：

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