Android中从assets资源中读取图片文件并保存到内部存储器并加载显示在ImageView中

桃扇骨 2023-10-05 14:53 40阅读 0赞

## 场景 ##

Android系统为每个新设计的程序提供了/assets目录，这个目录保存的文件可以打包在程序里。/res和/assets的不同点是，android不为/assets下的文件生成ID。如果使用/assets下的文件，需要指定文件的路径和文件名。assets 可以被看做随应用打包的微型文件系统，支持任意层次的文件目录结构。正因为这点，游戏这种需要加载大量图片和声音资源的应用通常都会使用它。assets目录中的所有文件都会随应用打包。assets类资源放在工程根目录的assets子目录下，它里面保存的是一些原始的文件，可以以任何方式来进行组织。这些文件最终会被原装不动地打包在apk文件中。如果我们要在程序中访问这些文件，那么就需要指定文件名来访问。

注：

博客：  
[https://blog.csdn.net/badao\_liumang\_qizhi][https_blog.csdn.net_badao_liumang_qizhi]  
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## 实现 ##

在res下右键New-Folder-Assets Folder

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70][]

然后确认assets的位置

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 1][]

点击Finish即可，然后在assets下添加一个文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 2][]

新建一个activity，并在布局xml文件中添加如下

<?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=".AssetsActivity">
    
        <Button
            android:id="@+id/btn_save"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="获取assets并保存到内部存储器"/>
    
        <Button
            android:id="@+id/btn_show"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="加载内部存储器照片并显示在ImageView"/>
    
        <ImageView
            android:id="@+id/imageview"
            android:layout_width="match_parent"
            android:layout_height="350dp"/>
    </LinearLayout>

然后修改activity的代码

package com.badao.androidstudy;
    
    import androidx.appcompat.app.AppCompatActivity;
    
    import android.content.Context;
    import android.content.res.AssetManager;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.ImageView;
    import android.widget.Toast;
    
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    
    public class AssetsActivity extends AppCompatActivity {
    
        private Button btn_save;
        private Button btn_show;
        private ImageView imageView;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_assets);
            btn_save = findViewById(R.id.btn_save);
            btn_show = findViewById(R.id.btn_show);
            imageView = findViewById(R.id.imageview);
    
            //实现将图片文件从assets资源文件夹中读取并保存到本机内部存储器中
            btn_save.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    AssetManager manager = getAssets();
                    InputStream is = null;
                    FileOutputStream fos = null;
                    try {
                        //采用边读边写的方式
                        is = manager.open("badao.png");
                        fos = openFileOutput("badao.png",Context.MODE_PRIVATE);
                        byte[] buffer = new byte[1024];
                        int len = -1;
                        while ((len = is.read(buffer)) !=-1)
                        {
                            fos.write(buffer,0,len);
                        }
                        Toast.makeText(AssetsActivity.this,"保存成功",Toast.LENGTH_LONG).show();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }finally {
                        if(fos!=null)
                        {
                            try {
                                fos.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                        if(fos!=null)
                        {
                            try {
                                fos.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            });
    
            //将图片从内部存储器中加载出来并显示在ImageView中
            btn_show.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String filePath = getFilesDir().getAbsolutePath()+"/badao.png";
                    Bitmap bitmap = BitmapFactory.decodeFile(filePath);
                    imageView.setImageBitmap(bitmap);
                }
            });
        }
    }

点击第一个按钮将assets下的图片保存到内部存储器中

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 3][]

然后会在data/data/包名/files下查看到保存的文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 4][]

然后点击第二个按钮从内部存储器中加载图片并显示在ImageView中

![20201202220138240.gif][]

[https_blog.csdn.net_badao_liumang_qizhi]: https://blog.csdn.net/badao_liumang_qizhi
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20201202220128931.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20201202220133542.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=,size_16,color_FFFFFF,t_70
[20201202220138240.gif]: https://img-blog.csdnimg.cn/20201202220138240.gif