場景

Android中點擊按鈕啟動另一個Activity以及Activity之間傳值：

https://blog.csdn.net/BADAO_LIUMANG_QIZHI/article/details/103919470

在上面啟動Activity和傳值之后，怎樣獲取Acitvity的回傳值，下面示例實作點擊選擇頭像按鈕，跳轉到頭像顯示Activity，并將選擇的圖片的索引回傳，在MainActivity中獲取后設定頭像，

效果

注：

博客：
https://blog.csdn.net/badao_liumang_qizhi
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實作

首先是主頁面MainActivity的布局，添加一個選擇頭像按鈕和一個ImageView用來顯示頭像，

<?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/image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>

<Button
    android:id="@+id/button"
    android:text="選擇頭像"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>

</LinearLayout>

然后在MainActivity中的OnCreate方法中，使用startActivityForResult能啟動另一個Activity并能獲得回傳結果，

要設定一個請求碼，這里是200，

        Button button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,HeadActivity.class);
                startActivityForResult(intent,200);
            }
        });

然后跳轉到第二個Activity用來選擇頭像，首先設定其布局檔案，添加一個GridView用來顯示要選擇的頭像照片，

activity_head.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=".HeadActivity">

    <GridView
        android:id="@+id/gridView"
        android:numColumns="4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

然后來到其Activity，使用配接器為其設定照片源，

首先宣告一個圖片陣列

    private  int[] imageId = new int[]{
        R.drawable.img1,R.drawable.img2
    };

這里參考了drawable下的兩張頭像照片，

然后使用配接器為照片設定資料源

        GridView gridView = (GridView) findViewById(R.id.gridView);
        BaseAdapter adapter = new BaseAdapter() {
            @Override
            public int getCount() {
                return imageId.length;
            }

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

            @Override
            public long getItemId(int position) {
                return 0;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                ImageView imageView;
                if(convertView ==null)
                {
                    imageView = new ImageView(HeadActivity.this);
                    imageView.setAdjustViewBounds(true);
                    imageView.setMaxWidth(158);
                    imageView.setMaxHeight(150);
                    imageView.setPadding(5, 5, 5, 5);

                }else
                {
                    imageView = (ImageView) convertView;
                }
                imageView.setImageResource(imageId[position]);
                return imageView;
            }
        };

        gridView.setAdapter(adapter);

然后在gridView的選項點擊事件監聽器中，獲取選中照片的索引并通過Bundle物件的putInt和intent物件的putExtras將資料進行回傳，然后呼叫 setResult(200,intent);將結果進行回傳，這里的請求結果碼也設定為200，

完整HeadActivity.java

package com.badao.selectimage;

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 {

    private  int[] imageId = new int[]{
        R.drawable.img1,R.drawable.img2
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {        GridView gridView = (GridView) findViewById(R.id.gridView);
        BaseAdapter adapter = new BaseAdapter() {
            @Override
            public int getCount() {
                return imageId.length;
            }

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

            @Override
            public long getItemId(int position) {
                return 0;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                ImageView imageView;
                if(convertView ==null)
                {
                    imageView = new ImageView(HeadActivity.this);
                    imageView.setAdjustViewBounds(true);
                    imageView.setMaxWidth(158);
                    imageView.setMaxHeight(150);
                    imageView.setPadding(5, 5, 5, 5);

                }else
                {
                    imageView = (ImageView) convertView;
                }
                imageView.setImageResource(imageId[position]);
                return imageView;
            }
        };

        gridView.setAdapter(adapter);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_head);

        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(200,intent);
                finish();
            }
        });
    }
}

然后回到MainActivity怎樣接受回傳的結果，

ctrl + O重寫方法 onActivityResult,如果請求碼和回傳結果碼都是200,首先通過

Bundle bundle  = data.getExtras();

獲取Bundle物件，

然后通過

int imageId = bundle.getInt("imageId");

獲取回傳的照片索引資料，

然后給ImageView設定照片源，

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode ==200 && resultCode == 200)
        {
            Bundle bundle  = data.getExtras();
            int imageId = bundle.getInt("imageId");
            ImageView imageView = (ImageView) findViewById(R.id.image);
            imageView.setImageResource(imageId);

        }
    }

MainActivity完整示例代碼

package com.badao.selectimage;

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

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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode ==200 && resultCode == 200)
        {
            Bundle bundle  = data.getExtras();
            int imageId = bundle.getInt("imageId");
            ImageView imageView = (ImageView) findViewById(R.id.image);
            imageView.setImageResource(imageId);

        }
    }

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

        Button button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,HeadActivity.class);
                startActivityForResult(intent,200);
            }
        });


    }
}

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Android中呼叫另一個Activity并回傳結果-以模擬選擇頭像功能為例

場景

效果

實作