StartActivityForResult的用法「建议收藏」

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当一个OneActivity跳转到TwoActivity时，TwoActivity关闭时要把数据传回到OneActivity，这个时候就得用到StartActivityForResult。

使用这个方法特别要注意的是：一个Activity中可能包含多个按钮，并调用多个startActivityForResult方法来打开不同的Activity处理业务，当这些新Activity关闭后，系统会调用前面的Activity的onActivityResult方法。为了知道该方法是由哪个请求结果所触发的，可利用requestCode标识，为了知道返回的数据来自于那个新的Activity，可利用resultCode标识。

接下来我们通过一个栗子进行讲解，效果图如下（1跳转到2把值传过去显示出来，2跳转回1把值传回来显示出来）：

由于上传图片受到限制，只能展现出两个界面的跳转。

1、布局文件就贴两个出来：activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:textSize="18sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/bt_onclick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Skip_TO_Two" />


</LinearLayout>

activity_two.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".TwoActivity">

    <TextView
        android:id="@+id/tv_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp" />

    <Button
        android:id="@+id/bt_two"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Skip_TO_One" />

    <Button
        android:id="@+id/bt_three"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Skip_To_Three" />
</LinearLayout>

activity_three.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".ThreeActivity">

    <TextView
        android:id="@+id/tv_three"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp" />

    <Button
        android:id="@+id/bt_threeOther"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Skip_To_Two" />
</LinearLayout>

2、java类：MainActivity.class

public class MainActivity extends AppCompatActivity {
    private Button mBtn;
    private TextView mText;


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

    private void initView() {
        mBtn = findViewById(R.id.bt_onclick);
        mText = findViewById(R.id.tv_text);
        mBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, TwoActivity.class);
                Bundle bundle = new Bundle();
                //用bundle传个key为oneContent，值为hello twoActivity到第二个界面
                bundle.putString("oneContent", "OneActivty->TwoActivity");
                intent.putExtras(bundle);
                startActivityForResult(intent, 0);
            }
        });

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == 1) {//接收后面一个界面结果码为1的界面
            Bundle bundle = data.getExtras();//注意这里是data,就是这个方法里面的Intent对象，这才是后面界面传回来的intent。
            String name = bundle.getString("twoContent");
            mText.setText(name);
        }

    }

}

TwoActivity.class

public class TwoActivity extends AppCompatActivity {
    private TextView mContent;
    private Button mSkip, mSkipToThree;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_two);
        mContent = findViewById(R.id.tv_text);
        mSkip = findViewById(R.id.bt_two);
        mSkipToThree = findViewById(R.id.bt_three);
        Intent intent = getIntent();//获取前一个activity的传值
        Bundle bundle = intent.getExtras();
        String name = bundle.getString("oneContent");//获取前一个界面key为oneContent的值
        mContent.setText(name);
        mSkip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent1 = new Intent(TwoActivity.this, MainActivity.class);
                Bundle bundle1 = new Bundle();
                bundle1.putString("twoContent", "TwoActivity->OneActivity");
                intent1.putExtras(bundle1);
                //把resultcode传回到前一个界面，并把intent1携带的值传回前一个界面
                setResult(1, intent1);
                finish();//记得要finish
            }
        });
        mSkipToThree.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent2 = new Intent(TwoActivity.this, ThreeActivity.class);
                Bundle bundle2 = new Bundle();
                bundle2.putString("threeContent", "TwoActivity->ThreeActivity");
                intent2.putExtras(bundle2);
                startActivityForResult(intent2, 3);
                Log.i("start", "start");
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == 4) {
            Bundle bundle = data.getExtras();
            String name = bundle.getString("ThreeContent");
            mContent.setText(name);
        }
    }
}

ThreeActivity.class

public class ThreeActivity extends AppCompatActivity {
    private TextView mContent;
    private Button mSkip;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_three);
        mContent = findViewById(R.id.tv_three);
        mSkip = findViewById(R.id.bt_threeOther);
        Intent intent =getIntent(); //获取前一个activity的传值
        Bundle bundle =intent.getExtras();
        Log.i("bundle","bundle="+bundle);
        String name = bundle.getString("threeContent");
        Log.i("name", "name="+name);
        mContent.setText(name);
        mSkip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent1 = new Intent();
                Bundle bundle1 = new Bundle();
                bundle1.putString("ThreeContent", "ThreeActivity->TwoActivity");
                intent1.putExtras(bundle1);
                setResult(4, intent1);
                finish();//记得要finish
            }
        });
    }
}