如何在Android中使用消息处理程序延迟运行循环？

Question

我正在尝试在Android应用中制作循环，这是由按钮点击触发的。 在阅读有关在SO（for example here）上进行循环/延迟的提示后，我决定使用消息处理程序方法而不是Runnable。

在下面的代码中，执行toastLoop（）并打印“以x开始”秒。 但是，该消息似乎没有发布该延迟。 或者，邮件已发布但处理程序未收到该邮件。 我是新手，我可能在某处犯了一个愚蠢的错误。 我在下面的代码中缺少什么？或者这段代码完全是愚蠢的？

    package com.example.testapp;

    import android.annotation.TargetApi;
    import android.content.Context;
    import android.os.Build;
    import android.os.Bundle;
    import android.os.Handler;
    import android.os.Message;
    import android.support.v4.app.FragmentActivity;
    import android.support.v4.app.NavUtils;
    import android.util.Log;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Toast;



    public class ExecActivity extends FragmentActivity {

        static Context context = null;
        String LOG_TAG = "FTR";
        static boolean test_status = false;
        ToastLoop toast_loop;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_exec);
            // Show the Up button in the action bar.
            setupActionBar();
        }

        /**
         * Set up the {@link android.app.ActionBar}, if the API is available.
         */
        @TargetApi(Build.VERSION_CODES.HONEYCOMB)
        private void setupActionBar() {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
                getActionBar().setDisplayHomeAsUpEnabled(true);
            }
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.exec, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()) {
            case android.R.id.home:
                // This ID represents the Home or Up button. In the case of this
                // activity, the Up button is shown. Use NavUtils to allow users
                // to navigate up one level in the application structure. For
                // more details, see the Navigation pattern on Android Design:
                //
                // http://developer.android.com/design/patterns/navigation.html#up-vs-back
                //
                NavUtils.navigateUpFromSameTask(this);
                return true;
            }
            return super.onOptionsItemSelected(item);
        }


        class ToastLoop {

            private final int loop_max_duration = 60; // in seconds

            final int TOAST = 1;
            Handler handler = new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    Log.i(LOG_TAG, "Handler(): msg: " + msg.what);
                    switch (msg.what) {        
                    case TOAST:
                        Toast.makeText( ExecActivity.this, "Doing my thing", Toast.LENGTH_SHORT).show();
                        if ( test_status) { // test is still running
                            toastLoop();
                        }
                        break;

                    default:
                        Toast.makeText(ExecActivity.this, "Unhandled", Toast.LENGTH_SHORT).show();
                        break;
                    }
                }
            };

            public boolean toastLoop() {
                if ( test_status) { // test is still running
                    long curr_time_milli = System.currentTimeMillis();
                    long window_position_sec = (long)( ((long)(curr_time_milli/1000))/loop_max_duration); // fraction discarded
                    long loop_start_time_sec = (window_position_sec + 1 ) * loop_max_duration;
                    long actual_start_time_milli = loop_start_time_sec * 1000;
                    Log.i(LOG_TAG, "toastLoop(): starting in " + ((actual_start_time_milli - curr_time_milli)/1000) );

                    Message msg = handler.obtainMessage( TOAST);
                    handler.sendMessageAtTime( msg, actual_start_time_milli );
                    return true;
                }
                return false;
            }

        }

        public boolean beginTest( View view) {
            Log.i(LOG_TAG, "in beginTest()");
            test_status = true;
            toast_loop = new ToastLoop();
            toast_loop.toastLoop();
            return true;
        }

        public boolean endTest( View view) {
            Log.i(LOG_TAG, "in endTest()");
            test_status = false;
            return true;
        }

    }