【070】Android 中相关功能的实现代码

☀.☀ ---<< 目录 >>-----

1. 点击两次back退出程序
2. 点击按钮后在状态栏显示通知实现
3. 用代码来布局控件的实现

☀.☀ ---<< 001. 点击两次back退出程序 >>-----

private long exitTime = 0;  
  
    @Override  
    public boolean onKeyDown(int keyCode, KeyEvent event) {  
        if (keyCode == KeyEvent.KEYCODE_BACK  
                && event.getAction() == KeyEvent.ACTION_DOWN) {  
  
            if ((System.currentTimeMillis() - exitTime) > 2000) {  
                Toast.makeText(getApplicationContext(), "再按一次退出程序",  
                        Toast.LENGTH_SHORT).show();  
                exitTime = System.currentTimeMillis();  
            } else {  
                finish();  
                System.exit(0);  
            }  
            return true;  
        }  
        return super.onKeyDown(keyCode, event);  
    }  

☀.☀ ---<< 002. 点击按钮后在状态栏显示通知实现 >>-----

效果：

1. 首先点击第一幅图的“Display Notification”按钮，接着在状态栏出现一条通知，如屏幕顶部所示。
2. 将状态栏往下拉，可以看到第二幅图显示的信息。
3. 点击第二幅图中的通知，会跳转到第三幅图中的 activity。

实现：

NotificationActivity.java

public class NotificationsActivity extends Activity {
    int notificationID = 1;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
    
    public void onClick(View view) {
        displayNotification();
    }
    
    protected void displayNotification()
    {
        //---PendingIntent to launch activity if the user selects
        // this notification---
        Intent i = new Intent(this, NotificationView.class);
        i.putExtra("notificationID", notificationID);

        PendingIntent pendingIntent =
            PendingIntent.getActivity(this, 0, i, 0);

        NotificationManager nm = (NotificationManager)
            getSystemService(NOTIFICATION_SERVICE); 

        Notification notif = new Notification(
            R.drawable.ic_launcher, 
            "Reminder: Meeting starts in 5 minutes",
            System.currentTimeMillis());

        CharSequence from = "System Alarm";
        CharSequence message = "Meeting with customer at 3pm...";
        
        notif.setLatestEventInfo(this, from, message, pendingIntent);

        //---100ms delay, vibrate for 250ms, pause for 100 ms and
        // then vibrate for 500ms---
        notif.vibrate = new long[] { 100, 250, 100, 500};
        nm.notify(notificationID, notif);        
    }
}

NotificationView.java

public class NotificationView extends Activity
{
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.notification);
            
        //---look up the notification manager service---
        NotificationManager nm = (NotificationManager) 
            getSystemService(NOTIFICATION_SERVICE);

        //---cancel the notification that we started--- 
        nm.cancel(getIntent().getExtras().getInt("notificationID"));
    }
}

源代码下载：Notifications.zip

☀.☀ ---<< 003. 用代码来布局控件的实现 >>-----

public class UICodeActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);
        //---param for views---
        LayoutParams params = 
            new LinearLayout.LayoutParams(
                LayoutParams.FILL_PARENT,
                LayoutParams.WRAP_CONTENT);

        //---create a layout---
        LinearLayout layout = new LinearLayout(this);
        layout.setOrientation(LinearLayout.VERTICAL);

        //---create a textview---
        TextView tv = new TextView(this);
        tv.setText("This is a TextView");
        tv.setLayoutParams(params);

        //---create a button---
        Button btn = new Button(this);
        btn.setText("This is a Button");
        btn.setLayoutParams(params);
                        
        //---adds the textview---
        layout.addView(tv);

        //---adds the button---
        layout.addView(btn);

        //---create a layout param for the layout---
        LinearLayout.LayoutParams layoutParam = 
            new LinearLayout.LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT );

        this.addContentView(layout, layoutParam);
    }
}

源代码下载：UICode.zip

☀.☀ ---<< 004. 点击两次back退出程序 >>-----

 

☀.☀ ---<< 005. 点击两次back退出程序 >>-----

 

☀.☀ ---<< 006. 点击两次back退出程序 >>-----