Android学习笔记（三）基础知识（2）

交互对话框

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使用Android SDK中，具有交互功能的对话框是AlertDialog窗口。

package com.example.test8;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.support.v4.app.NavUtils;

public class MainActivity extends Activity {

    private Button bt;
    int n=0;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        bt=(Button)findViewById(R.id.button1);
        bt.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                // TODO Auto-generated method stub
                n++;
                String str=Integer.toString(n);
                bt.setText("点击次数："+n);
                new AlertDialog.Builder(MainActivity.this)
                .setTitle("提示")
                .setMessage("对话框")
                .setPositiveButton("确定",new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                    }
                } )
                .show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}

拖放相片特效

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　　在Android中，拖动图片的特效可以通过Android.content.Context,Android,widget.BaseAdapter和Android.widget.imageView等来实现。

　　在下面的列子中，context可以像画布一样，随时可以被处理覆盖。Context是作为Android.content子类。通过widget.BaseAdapter作为容器来存放Gallery所需要的图片。 

　　这里是通过使用Gallery实现的相片拖拽功能，具体代码如下：

package com.example.test9;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.graphics.Color;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.TextView;
import android.support.v4.app.NavUtils;

public class MainActivity extends Activity {
    
    private TextView textview;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        textview = (TextView)findViewById(R.id.textView1);
        textview.setText("特效演示");
        textview.setTextColor(Color.BLUE);
        
        Gallery gallery=(Gallery)findViewById(R.id.gallery1);
        gallery.setAdapter(new ImageAdapter(this));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public class ImageAdapter extends BaseAdapter{

        private Context myContext;
        
        private int[] myImageID={android.R.drawable.btn_minus,
                android.R.drawable.btn_radio,
                android.R.drawable.ic_lock_idle_low_battery,
                android.R.drawable.ic_menu_camera
        };
        
        public ImageAdapter(Context c){
            this.myContext=c;
        }
        
        public int getCount() {
            // TODO Auto-generated method stub
            return this.myImageID.length;
        }

        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub
            ImageView i=new ImageView(this.myContext);
            
            i.setImageResource(this.myImageID[position]);
            i.setScaleType(ImageView.ScaleType.FIT_XY);
            
            i.setLayoutParams(new Gallery.LayoutParams(120,120));
            return i;
        }
        
    }
    
}

设置about关于信息

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 创建一个onCreateOptionsMenu(Menu menu)类函数，用于添加Menu菜单项，再利用onOptionItemSelected选择菜单项

package com.example.test10;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.app.NavUtils;

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        menu.add(0,0,0,"关于");
        menu.add(0,1,1,"退出");
        return super.onCreateOptionsMenu(menu);
    }

    public boolean onOptionsItemSelected(MenuItem item){
        super.onOptionsItemSelected(item);
        switch(item.getItemId()){
        case 0:
            openOptionsDialog();
            break;
        case 1:
            finish();
        }
        return true;
    }
    
    private void openOptionsDialog(){
        new AlertDialog.Builder(this)
        .setTitle("关于")
        .setMessage("***")
        .setPositiveButton("OK",new OnClickListener() {
            
            public void onClick(DialogInterface dialog, int which) {
                // TODO Auto-generated method stub
                
            }
        })
        .show();
    }
    
}

程序加载中状态框

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　　 程序加载中的提示，此功能是通过Progress Dialog类来运行，此类在Android.app.ProgressDialog类里。但是，我们需要注意使用dismiss()函数来关闭取得焦点的对话框，否则程序将陷入死循环，也不能在线程里更改CONTEXT或parent view的任何状态。

package com.example.test11;

import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.support.v4.app.NavUtils;

public class MainActivity extends Activity {

    private TextView text;
    private Button bt;
    public ProgressDialog myDialog=null;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        text=(TextView)findViewById(R.id.textView1);
        bt=(Button)findViewById(R.id.button1);
        
        bt.setOnClickListener(myShowProgressBar);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    Button.OnClickListener myShowProgressBar=new Button.OnClickListener() {
        public void onClick(View v) {
            // TODO Auto-generated method stub
            final CharSequence strDialogTile="请等待";
            final CharSequence strDialogBody="程序正在运行";
            
            myDialog=ProgressDialog.show(MainActivity.this,strDialogTile,strDialogBody,true);
            
            text.setText(strDialogBody);
            
            new Thread(){
                public void run(){
                    try{
                        text.setText("start");
                        sleep(3000);
                        text.setText("end");
                    }catch (Exception e) {
                        // TODO: handle exception
                        e.printStackTrace();
                    }
                    finally{
                        myDialog.dismiss();
                    }
                }
            }.start();
        }
    };
}