android.view.ViewRootImpl$CalledFromWrongThreadException错误处理
2015-01-24 13:00
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我们在编写android代码的时候,我们会将一些耗时的操作,比如网络访问、磁盘访问放到一个子线程中来执行。而这类操作往往伴随着UI的更新操作。比如说,访问网络加载一张图片
new Thread() { @Override public void run() { try { URL url = new URL(path); HttpURLConnection connection = (HttpURLConnection) url .openConnection(); // 设置请求方式 connection.setRequestMethod("GET"); // 设置超时时间 connection.setConnectTimeout(10000); int code
= connection.getResponseCode(); if (code == 200) { InputStream is = connection.getInputStream(); Bitmap bitmap = BitmapFactory.decodeStream(is); iv_beauty.setImageBitmap(bitmap); } else { Toast.makeText(getApplicationContext(), "图片获取失败!", 0).show(); } } catch
(Exception e) { Toast.makeText(getApplicationContext(), "图片获取失败!", 0) .show(); } } }.start();
如果是这样去操作,就会抛出
10-20 02:50:38.219: W/System.err(497): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
后边那句英文的大概是说只有创建了UI对象的主线程才能去修改UI
原因在于,在android里面不是线程安全的,所以android有阻止子线程更新组件的机制。
于是我们应该将UI的更新交给主线程来完成,如何去完成,android为我们提供了一套消息处理机制。
它大概的实现步骤是这样子的
1.子线程利用Handler类发送一条消息,消息会被送完主线程的消息队列里
2.主线程里边有一个叫looper的轮询器,它会循环遍历消息队列
3.如果loopler发现消息队列里有新的消息,android就会调用Handler的handleMessage()方法来处理消息
new Thread() { @Override public void run() { try { URL url = new URL(path); HttpURLConnection connection = (HttpURLConnection) url .openConnection(); // 设置请求方式 connection.setRequestMethod("GET"); // 设置超时时间 connection.setConnectTimeout(10000); int code
= connection.getResponseCode(); if (code == 200) { InputStream is = connection.getInputStream(); Bitmap bitmap = BitmapFactory.decodeStream(is); iv_beauty.setImageBitmap(bitmap); } else { Toast.makeText(getApplicationContext(), "图片获取失败!", 0).show(); } } catch
(Exception e) { Toast.makeText(getApplicationContext(), "图片获取失败!", 0) .show(); } } }.start();
如果是这样去操作,就会抛出
10-20 02:50:38.219: W/System.err(497): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
后边那句英文的大概是说只有创建了UI对象的主线程才能去修改UI
原因在于,在android里面不是线程安全的,所以android有阻止子线程更新组件的机制。
于是我们应该将UI的更新交给主线程来完成,如何去完成,android为我们提供了一套消息处理机制。
它大概的实现步骤是这样子的
1.子线程利用Handler类发送一条消息,消息会被送完主线程的消息队列里
2.主线程里边有一个叫looper的轮询器,它会循环遍历消息队列
3.如果loopler发现消息队列里有新的消息,android就会调用Handler的handleMessage()方法来处理消息
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