Android使用GridView异步加载（弱引用）网络图片（支持点击查看）

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在现在的Android开发中，越来越多的app都使用了Android的相册功能，使用相册就会用到GridView去加载图片，但是加载大量的图片的时候，会因为加载过程缓慢从而出现黑屏，而且因为图片越来越多从而引发出OOM的问题。这种情况就需要使用线程去异步加载图片并显示。

先看效果图：

• **
• 一个GridView控件
• 适配器
• 一个异步加载的自定义类
• 一个加载原图片的dialog
• **

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activity_mail.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"    tools:context="activity.cc.com.demo014.MainActivity"    android:orientation="vertical">    <GridView        android:id="@+id/gridview"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:numColumns="3"/></LinearLayout>

注：只包含一个GridView控件

MainActivity.java:

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_main);        //获取控件并实现点击事件        gridView = (GridView) findViewById(R.id.gridview);        gridView.setOnItemClickListener(this);        //getDatas方法是填充datas数据        getDatas();        //使用adapter填充数据        gridViewAdapter = new GridViewAdapter(this, datas, gridView);        gridView.setAdapter(gridViewAdapter);    }

GridViewAdapter.java:

package activity.cc.com.demo014;import android.app.Activity;import android.graphics.Bitmap;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.GridView;import android.widget.ImageView;import android.widget.TextView;import java.util.ArrayList;import java.util.List;/** * Created by admin on 2017/12/11. */public class GridViewAdapter extends BaseAdapter {    List<GridViewData> datas = new ArrayList<GridViewData>();    GridView gridview;    Activity activity;    LayoutInflater inflater;    AsyncImageLoader asyncImageLoader;    /**     * 实例化adapter并接收传递的数据     * @param activity     * @param datas     * @param gridview     */    public GridViewAdapter(Activity activity, List<GridViewData> datas, GridView gridview){        this.activity = activity;        this.datas = datas;        this.gridview = gridview;        //实例化LayoutInflater        inflater = activity.getLayoutInflater();        //实例化异步加载图片的类        asyncImageLoader = new AsyncImageLoader();    }    /**     * 这个方法是显示的图片的个数     * @return 取决于datas的大小     */    @Override    public int getCount() {        return datas.size();    }    /**     * 获取每一个item的数据     * @param position     * @return     */    @Override    public GridViewData getItem(int position) {        return datas.get(position);    }    /**     * getItemId     * @param position     * @return     */    @Override    public long getItemId(int position) {        return position;    }    /**     * 每加载一次系统调用一次     * @param position     * @param convertView     * @param parent     * @return     */    @Override    public View getView(int position, View convertView, ViewGroup parent) {        //当回收的view为空，重新获取        if(convertView == null){            convertView = inflater.inflate(R.layout.gridview_item, null);        }        convertView.setTag(position);        //拿到每一个item的值        GridViewData info = getItem(position);        //使用异步加载图片的类加载图片并实现回调        asyncImageLoader.loadDrawable(position, info.img_url, new AsyncImageLoader.ImageCallback() {            @Override            public void onImageLoad(Integer t, Bitmap bitmap) {                View view = gridview.findViewWithTag(t);                if(view != null){                    Log.i("TAG", "加载成功...");                    ImageView img_url = view.findViewById(R.id.img_url);                    img_url.setImageBitmap(bitmap);                }            }            @Override            public void onError(Integer t) {                View view = gridview.findViewWithTag(t);                if(view != null){                    Log.i("TAG", "加载失败...");                    ImageView img_url = view.findViewById(R.id.img_url);                    //加载中或者加载失败，默认加载app图标                    img_url.setBackgroundResource(R.mipmap.ic_launcher);                }            }        });        TextView txt_name = convertView.findViewById(R.id.txt_name);        txt_name.setText(info.name);        return convertView;    }}

GridViewData.java:

package activity.cc.com.demo014;/** * Created by admin on 2017/12/11. */public class GridViewData {    public GridViewData(String img_url, String name){        this.img_url = img_url;        this.name = name;    }    public String img_url, name;    public String getImg_url() {        return img_url;    }    public void setImg_url(String img_url) {        this.img_url = img_url;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "GridViewData{" +                "img_url='" + img_url + '\'' +                ", name='" + name + '\'' +                '}';    }}

注：注意属性值是public。到这里图片的异步加载就结束了。下来就是单击图片实现查看原图。

MainActivity.java:

@Overridepublic void onItemClick(AdapterView<?> parent, View view, int position, long id) {    Log.i("TAG", "" + position);    showImageDialog(position);}private void showImageDialog(int position) {    //弹出友好提示框，提示用户确认注销？    new CommomDialog(this, position, R.style.dialog, datas.get(position).getImg_url(), new CommomDialog.OnCloseListener() {        @Override        public void onClick(Dialog dialog, boolean confirm) {            if(confirm){                dialog.dismiss();            }        }    }).setTitle(datas.get(position).getName()).show();}

CommomDialog.java:

package activity.cc.com.demo014;import android.app.Dialog;import android.content.Context;import android.graphics.Bitmap;import android.os.Bundle;import android.text.TextUtils;import android.util.Log;import android.view.View;import android.widget.ImageView;import android.widget.TextView;/** * 封装的dialog */public class CommomDialog extends Dialog implements View.OnClickListener {    private TextView textview_name;    private ImageView image_url;    private Context mContext;    private String img_url;    private OnCloseListener listener;    private String positiveName;    private String negativeName;    private String title;    int position;    AsyncImageLoader asyncImageLoader;    public CommomDialog(Context context) {        super(context);        this.mContext = context;    }    public CommomDialog(Context context, int themeResId, String img_url) {        super(context, themeResId);        this.mContext = context;        this.img_url = img_url;    }    public CommomDialog(Context context, int position, int themeResId, String img_url, OnCloseListener listener) {        super(context, themeResId);        this.mContext = context;        this.position = position;        this.img_url = img_url;        this.listener = listener;        asyncImageLoader = new AsyncImageLoader();    }    protected CommomDialog(Context context, boolean cancelable, OnCancelListener cancelListener) {        super(context, cancelable, cancelListener);        this.mContext = context;    }    public CommomDialog setTitle(String title){        this.title = title;        return this;    }    public CommomDialog setPositiveButton(String name){        this.positiveName = name;        return this;    }    public CommomDialog setNegativeButton(String name){        this.negativeName = name;        return this;    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.imgae_view);        setCanceledOnTouchOutside(false);        initView();        initData();    }    private void initData() {        asyncImageLoader.loadDrawable(position, img_url, new AsyncImageLoader.ImageCallback() {            @Override            public void onImageLoad(Integer t, Bitmap bitmap) {                image_url.setImageBitmap(bitmap);            }            @Override            public void onError(Integer t) {                image_url.setBackgroundResource(R.mipmap.ic_launcher);            }        });        textview_name.setText(title);    }    private void initView(){        image_url = findViewById(R.id.image_url);        textview_name = findViewById(R.id.textview_name);        image_url.setOnClickListener(this);    }    @Override    public void onClick(View v) {        int temdId = v.getId();        if(temdId == R.id.image_url){            dismiss();        }//        switch (v.getId()){//            case R.id.cancel://                if(listener != null){//                    listener.onClick(this, false);//                }//                this.dismiss();//                break;//            case R.id.submit://                if(listener != null){//                    listener.onClick(this, true);//                }//                break;//        }    }    public interface OnCloseListener{        void onClick(Dialog dialog, boolean confirm);    }}

imgae_view.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"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="#FFFFFF" >    <TextView        android:id="@+id/textview_name"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center"        android:text="TextView"        android:textColor="#000000" />    <ImageView        android:id="@+id/image_url"        android:layout_width="match_parent"        android:layout_height="wrap_content"        app:srcCompat="@mipmap/ic_launcher" /></LinearLayout>

注：至此为止，功能就已经实现了。

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优化：这里显示的图片是按照原尺寸显示的，如果需要固定大小并且充满布局，在ImageView控件上加上android:scaleType=”fitXY”这行代码就好。

GAME OVER！！！

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