startActivityForResult调用另外一个Activity获取返回结果

startActivityForResult(intent,requestCode)可以调用另外一个Activity，并返回结果。

换头像案例

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">
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center"
        android:src="@drawable/tx"/>
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="选择头像"
        android:textSize="26sp"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".HeadActivity">
    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="10dp"
        android:horizontalSpacing="3dp"
        android:verticalSpacing="3dp"
        android:numColumns="4"/>
</RelativeLayout>

MainActivity.java

package com.example.startactivityforresult;

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

import android.content.Intent;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,
                        HeadActivity.class);
                startActivityForResult(intent,0x11);
            }
        });
    }
    /**该方法用于获取返回结果**/
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        //判断请求码和返回码是不是一致
        if (requestCode == resultCode){
            Bundle bundle = data.getExtras();
            int imageId = bundle.getInt("imageId");
            ImageView imageView = (ImageView) findViewById(R.id.imageView);
            imageView.setImageResource(imageId);
        }
    }
}

HeadActivity.java

package com.example.startactivityforresult;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class HeadActivity extends AppCompatActivity {

    public int[] imageId = new int[]{
            R.drawable.tx1,R.drawable.tx2,R.drawable.tx3,R.drawable.tx4
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_head);
        GridView gridView = (GridView) findViewById(R.id.gridView);

        BaseAdapter adapter = new BaseAdapter() {
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                ImageView imageview;
                if(convertView == null){
                    imageview = new ImageView(HeadActivity.this);
                    imageview.setAdjustViewBounds(true);
                    imageview.setMaxHeight(150);
                    imageview.setPadding(5,5,5,5);
                }else{
                    imageview = (ImageView)convertView;
                }
                imageview.setImageResource(imageId[position]);
                return imageview;
            }

            @Override
            public Object getItem(int position) {
                return position;
            }

            @Override
            public long getItemId(int position) {
                return position;
            }

            @Override
            public int getCount() {
                return imageId.length;
            }
        };

        gridView.setAdapter(adapter);
        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent intent = getIntent();
                Bundle bundle = new Bundle();
                bundle.putInt("imageId",imageId[position]);
                intent.putExtras(bundle);
                setResult(0x11,intent);
                finish();
            }
        });
    }
}

效果: