Android 利用代碼在屏幕中間位置顯示ProgressDialog和ProgressBar

package cc.testprogressdialog;

import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
/**
 * Demo描述:
 * 利用代碼在屏幕中間位置顯示ProgressDialog和ProgressBar
 * 
 * 參考資料:
 * 1 http://blog.csdn.net/lfdfhl/article/details/18913435
 * 2 http://blog.csdn.net/lfdfhl/article/details/9299075
 * 3 http://rocye.iteye.com/blog/1258936
 *   Thank you very much
 *   
 * 如果在某個線性布局中動態添加一個控件,並且想讓該控件在布局中居中.
 * 也可采用createProgressBar()方法中類似的方式
 *
 */
public class MainActivity extends Activity {
    private Context mContext;
    private ProgressBar mProgressBar;
    private ProgressDialog mProgressDialog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //顯示ProgressBar
        createProgressBar();
        //顯示ProgressDialog
        //createProgressDialog();
    }
    
    private void createProgressBar(){
        mContext=this;
        //整個Activity布局的最終父布局,參見參考資料
        FrameLayout rootFrameLayout=(FrameLayout) findViewById(android.R.id.content);
        FrameLayout.LayoutParams layoutParams=
        new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
        layoutParams.gravity=Gravity.CENTER;
        mProgressBar=new ProgressBar(mContext);
        mProgressBar.setLayoutParams(layoutParams);
        mProgressBar.setVisibility(View.VISIBLE);
        rootFrameLayout.addView(mProgressBar);
    }
    
    
    private void createProgressDialog(){
        mContext=this;
        mProgressDialog=new ProgressDialog(mContext);
        mProgressDialog.setMessage("...請您稍等...");
        mProgressDialog.show();
    }

}