版权声明：心灵泽尘 https://blog.csdn.net/github_38313789/article/details/83757051
package com.gaozewen.netimageviewer;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private static final int LOAD_IMAGE = 1;
private static final int LOAD_ERROR = 2;
private ImageView iv;
private List<String> paths;
private int currentPosition = 0;
// UIThread 主线程 ↓
private Handler mHandler = new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {
switch (msg.what){
case LOAD_IMAGE:
Bitmap bitmap = (Bitmap) msg.obj;
iv.setImageBitmap(bitmap);
Toast.makeText(MainActivity.this,"加载图片成功", Toast.LENGTH_SHORT).show();
break;
case LOAD_ERROR:
Toast.makeText(MainActivity.this,"加载图片失败", Toast.LENGTH_SHORT).show();
break;
}
return true;
}
});
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
iv = (ImageView) findViewById(R.id.iv);
// 1.链接服务器，获取所有的图片链接信息
loadAllImagePath();
}
// 获取全部图片资源路径
private void loadAllImagePath() {
new Thread() {
@Override
public void run() {
// 获取服务器数据
try {
URL url = new URL("http://192.168.1.102:8080/img/gaga.html");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET"); // 注意 GET 请求必须大写
int code = conn.getResponseCode();
if (code == 200) { // 返回成功
InputStream is = conn.getInputStream();
File file = new File(getCacheDir(), "info.txt");
FileOutputStream fos = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int len = 0;
while ((len = is.read(buffer)) != -1) {
fos.write(buffer, 0, len);
}
fos.flush();
fos.close();
is.close();
beginLoadImage();
} else if (code == 404) {
Message msg = Message.obtain();
msg.what = LOAD_ERROR;
msg.obj = "获取html失败，返回码：" + code;
mHandler.sendMessage(msg);
}else {
Message msg = Message.obtain();
msg.what = LOAD_ERROR;
msg.obj = "服务器异常，返回码：" + code;
mHandler.sendMessage(msg);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
// 开始加载图片，在从服务器获取完毕图片资源路径之后执行
private void beginLoadImage() {
try {
paths = new ArrayList<>();
File file = new File(getCacheDir(), "info.txt");
FileInputStream fis = new FileInputStream(file);
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
String line;
while ((line = br.readLine()) != null) {
paths.add(line);
}
br.close();
fis.close();
loadImageByPath(paths.get(currentPosition));
} catch (Exception e) {
e.printStackTrace();
}
}
//
private void loadImageByPath(final String path) {
new Thread() {
@Override
public void run() {
try {
File file = new File(getCacheDir(), path.replace("/", "") + ".jpg");
if (file.exists() && file.length() > 0){ // 缓存中有文件
System.out.println("通过缓存把图片获取出来...");
Message msg = Message.obtain();
msg.what = LOAD_IMAGE;
msg.obj = BitmapFactory.decodeFile(file.getAbsolutePath());
mHandler.sendMessage(msg);
// 安卓消息循环机制
// Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
// iv.setImageBitmap(bitmap);
/**
* 创建子线程 消息循环！！！！
*/
// UIThread 被创建之后就自带了一个 Looper，
// 这个 Looper 管理自身的 MessageQueue ,
// 其他创建出来的子线程 默认没有 Looper，
// 只能调用 Looper.prepare 和 Looper.loop 方法来进行消息循环
// 并且要 new 一个 Handler 对象来处理取出的 Message 对象
/*Looper.prepare();
mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
Toast.makeText(MainActivity.this,"加载图片完成" + msg.what, Toast.LENGTH_SHORT).show();
}
};
Message msg = Message.obtain();
msg.what = 100;
mHandler.sendMessage(msg);
Looper.loop();*/
}else { // 缓存中没文件
System.out.println("通过访问网络把图片资源获取出来...");
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
int code = conn.getResponseCode();
if(code == 200){
InputStream is = conn.getInputStream();
// 暂存在内存里的 图片
Bitmap bitmap = BitmapFactory.decodeStream(is);
// 将这个图片写入到 cache 文件夹中
FileOutputStream fos = new FileOutputStream(file);
bitmap.compress(Bitmap.CompressFormat.JPEG,100,fos);
fos.close();
is.close();
Message msg = Message.obtain();
msg.what = LOAD_IMAGE;
msg.obj = BitmapFactory.decodeFile(file.getAbsolutePath());
mHandler.sendMessage(msg);
}else {
/*Looper.prepare();
mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
Toast.makeText(MainActivity.this,"获取失败", Toast.LENGTH_SHORT).show();
}
};
Looper.loop();*/
Message msg = Message.obtain();
msg.what = LOAD_ERROR;
msg.obj = "获取图片失败，返回码：" + code;
mHandler.sendMessage(msg);
}
}
} catch (Exception e) {
e.printStackTrace();
Message msg = Message.obtain();
msg.what = LOAD_ERROR;
msg.obj = "获取图片失败,抛异常！！" ;
mHandler.sendMessage(msg);
}
}
}.start();
}
public void pre(View view) {
currentPosition--;
if (currentPosition < 0){
currentPosition = paths.size() -1;
}
loadImageByPath(paths.get(currentPosition));
}
public void next(View view) {
currentPosition++;
if (currentPosition >= paths.size()){
currentPosition = 0;
}
loadImageByPath(paths.get(currentPosition));
}
}