Android图片查看器

转载请标明出处：http://blog.csdn.net/wu_wxc/article/details/53705885
本文出自【吴孝城的CSDN博客】

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:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
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="cn.wuxiaocheng.pictureviewer.MainActivity">
<EditText
 android:id="@+id/et_imgurl"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="请输入图片url" />
<Button
 android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="click"
android:text="查看" />
<ImageView
 android:id="@+id/img_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="30dp" />
</LinearLayout>

MainActivity.java

package cn.wuxiaocheng.pictureviewer;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Base64;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private EditText etImageUrl;
private ImageView imageView;
private static final int MSG_CACHE_PIC = 1;
private static final int MSG_NEW_PIC = 2;
private static final int ERROR = 3;
private static final int EXCEPTION = 4;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etImageUrl = (EditText) findViewById(R.id.et_imgurl);
        imageView = (ImageView) findViewById(R.id.img_view);
    }
public void click(View v) {
final String url = etImageUrl.getText().toString();
// 用TextUtils.isEmpty()判断是否为空
if (TextUtils.isEmpty(url)) {
            Toast.makeText(MainActivity.this, "图片路径不能为空", Toast.LENGTH_SHORT).show();
return;
        }
new Thread() {
@Override
public void run() {
                getImage(url);
            }
        }.start();
    }
private void getImage(String url) {
// getCacheDir()会将图片放在data/data/包名/cache下
        File file = new File(getCacheDir(), Base64.encodeToString(url.getBytes(), Base64.DEFAULT));
// 如果图片存在
if (file.exists() && file.length() > 0) {
            System.out.println("文件存在，拿缓存");
// decodeFile可以将手机系统里的图片文件转换成Bitmap对象
// getAbsolutePath()拿到文件的绝对路径
            Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
// 声明消息，更新UI
            Message msg = new Message();
            msg.what = MSG_CACHE_PIC;
// 设置参数
            msg.obj = bitmap;
            handler.sendMessage(msg);
        } else {
// 图片不存在获取图片生成缓存
try {
                HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
int code = conn.getResponseCode();
if (code == 200) {
// png的图片
                    InputStream is = conn.getInputStream();
                    FileOutputStream fos = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int len = 0;
while ((len = is.read(buffer)) != -1) {
// 写入图片字节
                        fos.write(buffer, 0, len);
                    }
                    is.close();
                    fos.close();
                    Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
// 重写UI
                    Message msg = new Message();
                    msg.what = MSG_NEW_PIC;
                    msg.obj = bitmap;
                    handler.sendMessage(msg);
                } else {
//请求失败
                    Message msg = new Message();
                    msg.what = ERROR;
                    handler.sendMessage(msg);
                }
            } catch (IOException e) {
                e.printStackTrace();
// 发生异常，请求失败
                Message msg = new Message();
                msg.what = EXCEPTION;
                handler.sendMessage(msg);
            }
        }
    }
// 在主线程中声明消息处理机制handler
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_CACHE_PIC:
                    Bitmap bitmap = (Bitmap) msg.obj;
                    imageView.setImageBitmap(bitmap);
                    System.out.println("缓存的图片");
break;
case MSG_NEW_PIC:
                    Bitmap bitmap1 = (Bitmap) msg.obj;
                    imageView.setImageBitmap(bitmap1);
                    System.out.println("下载图片");
break;
case ERROR:
                    Toast.makeText(MainActivity.this, "请求失败", Toast.LENGTH_SHORT).show();
break;
case EXCEPTION:
                    Toast.makeText(MainActivity.this, "发生异常", Toast.LENGTH_SHORT).show();
break;
            }
        }
    };
}