ImageLoader简单使用

1.导包

 implementation 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'

2.权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.imageloader2">


    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

    <application
        android:name=".MyApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

3.初始化

package com.example.imageloader2;

import android.app.Application;

import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;

public class MyApplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        ImageLoaderConfiguration configuration = ImageLoaderConfiguration.createDefault(this);
        ImageLoader.getInstance().init(configuration);
    }
}

4.使用

注意：要先申请存储权限，否则可能出现图片下载失败

package com.example.imageloader2;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.GridView;
import com.nostra13.universalimageloader.core.ImageLoader;
import java.util.Arrays;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    private GridView mGridView;
    private ImageAdapter mImageAdapter;
    private String[] mImages = new String[]{
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg",
            "https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2477101223,88513767&fm=26&gp=0.jpg"
    };

    private List<String> mImageList;
    private boolean isGridViewIdle = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mImageList = Arrays.asList(mImages);
        mImageAdapter = new ImageAdapter(this, mImageList);
        mGridView = (GridView)findViewById(R.id.grid_view);
        mGridView.setOnScrollListener(new AbsListView.OnScrollListener(){

            @Override
            public void onScrollStateChanged(AbsListView absListView, int i) {
                if(i == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
                    isGridViewIdle = true;
                    mImageAdapter.notifyDataSetChanged();
                }else {
                    isGridViewIdle = false;
                }
            }

            @Override
            public void onScroll(AbsListView absListView, int i, int i1, int i2) {

            }
        });
        mGridView.setAdapter(mImageAdapter);
        //确认存储权限
        boolean exit = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED;
        if(!exit) {
            requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        boolean permit = true;
        for(int result : grantResults){
            if(result == -1) {
                permit = false;
                break;
            }
        }
        Log.d(TAG, "permit-:"+permit);
        if(permit) {
            mImageAdapter.notifyDataSetChanged();
        }
    }


    class ImageAdapter extends BaseAdapter {
        private Context mContext;
        private List mImages;

        public ImageAdapter(Context mContext, List mImages) {
            this.mContext = mContext;
            this.mImages = mImages;
        }

        @Override
        public int getCount() {
            return mImages.size();
        }

        @Override
        public Object getItem(int i) {
            return mImages.get(i);
        }

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

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            ViewHolder holder = null;
            if(view == null) {
                view = getLayoutInflater().inflate(R.layout.image_item, null);
                holder = new ViewHolder();
                holder.imageView = view.findViewById(R.id.square_item);
                view.setTag(holder);
            }else {
                holder = (ViewHolder) view.getTag();
            }
            final String uri = (String) getItem(i);
            ImageView imageView = holder.imageView;

            /*final String tag = (String) holder.imageView.getTag();
            if(uri.equals(tag)) {
                imageView.setImageResource(R.drawable.ic_launcher_background);
            }
            if(isGridViewIdle) {
                imageView.setTag(uri);
                ImageLoader.getInstance().displayImage(uri, imageView);
            }*/

            if(isGridViewIdle) {
                ImageLoader.getInstance().displayImage(uri, imageView);
            }
            return view;
        }

        class ViewHolder {
            SquareImageView imageView;
        }
    }
}

5.布局

activity_main.xml

 <?xml version="1.0" encoding="utf-8"?>

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity"
     android:orientation="vertical">
 
     <GridView
         android:id="@+id/grid_view"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:gravity="center"
         android:horizontalSpacing="5dp"
         android:verticalSpacing="5dp"
         android:listSelector="@android:color/transparent"
         android:numColumns="3"
         android:stretchMode="columnWidth"
         android:visibility="visible"/>
 
 </LinearLayout>

image_item.xml

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:gravity="center">
 
     <com.example.imageloader2.SquareImageView
         android:id="@+id/square_item"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:scaleType="centerCrop"
         android:src="@mipmap/ic_launcher"/>
 
 </LinearLayout>

6.自定义宽高相同的ImageView

package com.example.imageloader2;

import android.content.Context;
import android.util.AttributeSet;
import androidx.annotation.Nullable;

public class SquareImageView extends androidx.appcompat.widget.AppCompatImageView {
    public SquareImageView(Context context) {
        super(context);
    }

    public SquareImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public SquareImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, widthMeasureSpec);
    }
}

原文链接：https://blog.csdn.net/superman003008/article/details/114386265

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