android Activity runOnUiThread() 方法的使用

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利用Activity.runOnUiThread(Runnable)把更新ui的代码创建在Runnable中，然后在需要更新ui时，把这个Runnable对象传给Activity.runOnUiThread(Runnable).

Runnable对像就能在ui程序中被调用。

/**

 * Runs the specified action on the UI thread. If the current thread is the UI

 * thread, then the action is executed immediately. If the current thread is

 * not the UI thread, the action is posted to the event queue of the UI thread.

 *

 * @param action the action to run on the UI thread

 */

public final void runOnUiThread(Runnable action) {

    if (Thread.currentThread() != mUiThread) {

        mHandler.post(action);

    } else {

        action.run();

    }

}

从上面的源代码中可以看出，程序首先会判断当前线程是否是UI线程，如果是就直接运行，如果不是则post，这时其实质还是使用的Handler机制来处理线程与UI通讯。

        private ProgressDialog progressDialog;
        Context mContext；

        progressDialog = new ProgressDialog(mContext);
        String stri = mContext.getResources().getString(R.string.Is_sending_a_request);
        progressDialog.setMessage(stri);
        progressDialog.setCanceledOnTouchOutside(false);
        progressDialog.show();

        new Thread(new Runnable() {
            public void run() {
                try {
                       ((Activity)mContext).runOnUiThread(new Runnable() {
                        public void run() {
                            progressDialog.dismiss();
                            String s1 = mContext.getResources().getString(R.string.send_successful);
                            Toast.makeText(mContext, s1, Toast.LENGTH_LONG).show();
                        }
                    });
                } catch (final Exception e) {
                    ((Activity)mContext).runOnUiThread(new Runnable() {
                        public void run() {
                            progressDialog.dismiss();
                            String s2 = mContext.getResources().getString(R.string.Request_add_buddy_failure);
                            Toast.makeText(mContext, s2 + e.getMessage(), Toast.LENGTH_LONG).show();
                        }
                    });
                }
            }
        }).start();

用这种方式创建ProgressDialog就比较方便，或者刷新adapter也比使用Thread+Handler方便。

如果不是在activity中创建，需要在前面加上((Activity)mContext). 。