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"/><applicationandroid: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 {@Overridepublic 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;@Overrideprotected 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(){@Overridepublic void onScrollStateChanged(AbsListView absListView, int i) {if(i == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {isGridViewIdle = true;mImageAdapter.notifyDataSetChanged();}else {isGridViewIdle = false;}}@Overridepublic 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);}}@Overridepublic 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;}@Overridepublic int getCount() {return mImages.size();}@Overridepublic Object getItem(int i) {return mImages.get(i);}@Overridepublic long getItemId(int i) {return i;}@Overridepublic 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"><GridViewandroid: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.SquareImageViewandroid: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);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, widthMeasureSpec);}
}

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