安卓开发：SmartImageView简单实现和应用

package org.dreamtech.smartimageview;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.widget.ImageView;

public class MySmartImageView extends ImageView {

    protected static final int REQUESTSUCCESS = 1;
    protected static final int REQUESTFAIL = 2;
    protected static final int ERROR = 3;

    @SuppressLint("HandlerLeak")
    private Handler handler = new Handler() {

        public void handleMessage(android.os.Message msg) {

            switch (msg.what) {
            case REQUESTSUCCESS:
                Bitmap bitmap = (Bitmap) msg.obj;

                MySmartImageView.this.setImageBitmap(bitmap);

                break;

            case REQUESTFAIL:

                int default_resource = (Integer) msg.obj;
                MySmartImageView.this.setBackgroundResource(default_resource);

                break;

            case ERROR:
                int resource = (Integer) msg.obj;
                MySmartImageView.this.setBackgroundResource(resource);
                break;
            }

        };
    };

    // The construction methods of the parent class
    public MySmartImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public MySmartImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MySmartImageView(Context context) {
        super(context);
    }

    // A method of displaying pictures
    // path:The parameters of URL transmission
    public void setImageUrl(final String path) {
        new Thread() {
            public void run() {

                try {
                    URL url = new URL(path);

                    HttpURLConnection conn = (HttpURLConnection) url
                            .openConnection();
                    conn.setRequestMethod("GET");
                    conn.setConnectTimeout(5000);
                    int code = conn.getResponseCode();
                    if (code == 200) {
                        InputStream in = conn.getInputStream();

                        Bitmap bitmap = BitmapFactory.decodeStream(in);

                        Message msg = Message.obtain();
                        msg.obj = bitmap;
                        handler.sendMessage(msg);

                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

            };
        }.start();
    }

    // A method of displaying pictures(Overloading method)
    // path:The parameters of URL transmission
    // resource:Default resources(If you can‘t find a resource through this URL)
    public void setImageUrl(final String path, final int resource) {

        new Thread() {
            public void run() {

                try {
                    URL url = new URL(path);
                    HttpURLConnection conn = (HttpURLConnection) url
                            .openConnection();
                    conn.setRequestMethod("GET");
                    conn.setConnectTimeout(5000);
                    int code = conn.getResponseCode();
                    if (code == 200) {
                        InputStream in = conn.getInputStream();

                        Bitmap bitmap = BitmapFactory.decodeStream(in);
                        Message msg = Message.obtain();
                        msg.what = REQUESTSUCCESS;
                        msg.obj = bitmap;
                        handler.sendMessage(msg);

                    } else {
                        Message msg = Message.obtain();
                        msg.what = REQUESTFAIL;
                        msg.obj = resource;
                        handler.sendMessage(msg);
                    }
                } catch (Exception e) {
                    Message msg = Message.obtain();
                    msg.what = ERROR;
                    msg.obj = resource;
                    handler.sendMessage(msg);
                }

            };
        }.start();

    }

}

package org.dreamtech.smartimageview;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

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

        MySmartImageView iv = (MySmartImageView) findViewById(R.id.iv);

        iv.setImageUrl(
                "http://fanyi.bdstatic.com/static/translation/img/header/logo_cbfea26.png",
                R.drawable.default_ic);
    }

}

<RelativeLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <org.dreamtech.smartimageview.MySmartImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
         />

</RelativeLayout>