實現編輯文字(EditText)的清除按鈕

實例:

package com.AndroidEditText;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class AndroidEditTextActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        final EditText input = (EditText)findViewById(R.id.input);
        Button buttonClear = (Button)findViewById(R.id.clear);
        buttonClear.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    input.setText("");
   }});

    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<RelativeLayout 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content">
<Button
 android:id="@+id/clear"
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:hint="CLEAR" 
    android:layout_alignParentRight="true"/>
<EditText  
 android:id="@+id/input"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:hint="請輸入" 
    android:layout_alignParentLeft="true"
    android:layout_toLeftOf="@id/clear"/>

</RelativeLayout>
</LinearLayout>

顯示編輯文字的提示字

可使用 android:hint 標記設置顯示編輯文字的提示字.

實例:

<EditText  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:hint="請輸入" />

通過 Java 代碼設定 layout_width 為 50％

參考前文"怎麼設定layout_width為50％", 我們可以設置 <Button> 的重量參數(weight)設定 layout_width 為 50％.

但當我們使用 Java 代碼, 如果定義按鈕的 LayoutParams 為 LayoutParams, 我們是不能設置重量參數(weight)的!

可以把按鈕的 LayoutParams 定義為 LinearLayout.LayoutParams, 便可以通過 new LinearLayout.LayoutParams() 或 LinearLayout.LayoutParams.weight 設置重量參數(weight).

package com.AndroidWeight;

import android.app.Activity;
import android.os.Bundle;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.LinearLayout;

public class AndroidWeightActivity extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
  
  LinearLayout layout = new LinearLayout(getApplicationContext());
  layout.setOrientation(LinearLayout.HORIZONTAL);
  
  // Half Button 1
  LinearLayout subLayout1 = new LinearLayout(getApplicationContext());
  LinearLayout.LayoutParams paramsSubLayout1
   = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT, 1.0f);
  subLayout1.setLayoutParams(paramsSubLayout1);
  subLayout1.setOrientation(LinearLayout.VERTICAL);
  
  Button buttonHalfWidth1 = new Button(getApplicationContext());
  buttonHalfWidth1.setText("Half Width 1");
  LayoutParams paramsHalfWidth1
   = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT);
  buttonHalfWidth1.setLayoutParams(paramsHalfWidth1);
  
  // Half Button 2
  Button buttonHalfWidth2 = new Button(getApplicationContext());
  buttonHalfWidth2.setText("Half Width 2");
  LinearLayout.LayoutParams paramsHalfWidth2
   = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT);
  paramsHalfWidth2.weight = 1.0f;
  buttonHalfWidth2.setLayoutParams(paramsHalfWidth2);
    
  //--------
  subLayout1.addView(buttonHalfWidth1);
  layout.addView(subLayout1);
  layout.addView(buttonHalfWidth2);
  
  setContentView(layout);
   }
}

在標題欄顯示圖標(icon) - Window.FEATURE_LEFT_ICON/Window.FEATURE_RIGHT_ICON

要在標題欄顯示圖標, 先要要求窗口功能 Window.FEATURE_LEFT_ICON 和/或 Window.FEATURE_RIGHT_ICON:
requestWindowFeature(Window.FEATURE_LEFT_ICON);
requestWindowFeature(Window.FEATURE_RIGHT_ICON);

再調用 setFeatureDrawableResource() 方法來設定它.

實例:

package com.AndroidTitleIcon;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;

public class AndroidTitleIconActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_LEFT_ICON);
        requestWindowFeature(Window.FEATURE_RIGHT_ICON);
        setContentView(R.layout.main);
        getWindow().setFeatureDrawableResource(Window.FEATURE_LEFT_ICON,R.drawable.icon);
        getWindow().setFeatureDrawableResource(Window.FEATURE_RIGHT_ICON,R.drawable.icon);
    }
}

在標題欄顯示進度圖標 - Window.FEATURE_INDETERMINATE_PROGRESS

要在標題欄顯示進度圖標, 先要要求窗口功能"Window.FEATURE_INDETERMINATE_PROGRESS":
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);

再調用 setProgressBarIndeterminateVisibility(true/false) 方法來顯示/隱藏它.

實例:

package com.AndroidProgressTitleBar;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;

public class AndroidProgressTitleBarActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.main);
        
        Button btnTurnOnProgress = (Button)findViewById(R.id.progresson);
        Button btnTurnOffProgress = (Button)findViewById(R.id.progressoff);
        
        btnTurnOnProgress.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    setProgressBarIndeterminateVisibility(true);
   }});
        
        btnTurnOffProgress.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    setProgressBarIndeterminateVisibility(false);
   }});
    }
}

利用程式碼更改文字顏色, setTextColor()

實例:

package com.AndroidText;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class AndroidTextActivity extends Activity {
 
 TextView text;
 Button buttonChangeTextColor;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        text = (TextView)findViewById(R.id.text);
        buttonChangeTextColor = (Button)findViewById(R.id.changetextcolor);
     
        buttonChangeTextColor.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    
    /*
     * setTextColor(
     *  ((alpha << 24) & 0xFF000000)
     *  + ((red << 16) & 0x00FF0000)
     *  + ((green << 8) & 0x0000FF00)
     *  + (blue & 0x000000FF));
     */

    
    //setTypeface for TextView
    text.setTextColor(0xFF008080); 
    //setTypeface for Button
    buttonChangeTextColor.setTextColor(0xFFFF0000);
   }});
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:id="@+id/text"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button
    android:id="@+id/changetextcolor"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="Change Text Color"
    />
</LinearLayout>

動態改變文字的字體, setTypeface(typeface, style)

我們可以使用 Java 碼, 調用 setTypeface() 方法, 改變文字的字體.

textview.setTypeface(typeface, style)

其中 typeface 參數可以是:
- Typeface.DEFAULT
- Typeface.DEFAULT_BOLD
- Typeface.MONOSPACE
- Typeface.SANS_SERIF
- Typeface.SERIF

style 參數可以是:
- Typeface.BOLD
- Typeface.BOLD_ITALIC
- Typeface.ITALIC
- Typeface.NORMAL

實例:

package com.AndroidText;

import android.app.Activity;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class AndroidTextActivity extends Activity {
 
 TextView text;
 Button buttonChangeTypeFace;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        text = (TextView)findViewById(R.id.text);
        buttonChangeTypeFace = (Button)findViewById(R.id.changetypeface);
     
        buttonChangeTypeFace.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    
    /*
     * setTypeface(typeface, style)
     * typeface:
     * - Typeface.DEFAULT
     * - Typeface.DEFAULT_BOLD
     * - Typeface.MONOSPACE
     * - Typeface.SANS_SERIF
     * - Typeface.SERIF
     * 
     * style:
     * - Typeface.BOLD
     * - Typeface.BOLD_ITALIC
     * - Typeface.ITALIC
     * - Typeface.NORMAL
     */

    
    //setTypeface for TextView
    text.setTypeface(Typeface.MONOSPACE, Typeface.BOLD); 
    //setTypeface for Button
    buttonChangeTypeFace.setTypeface(Typeface.SANS_SERIF, Typeface.BOLD_ITALIC);
   }});
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:id="@+id/text"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button
    android:id="@+id/changetypeface"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="Change Typeface"
    />
</LinearLayout>

動態改變文字的大小, setTextSize()

實例:

package com.AndroidText;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class AndroidTextActivity extends Activity {
 
 TextView text;
 Button buttonChangeTextSize;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        text = (TextView)findViewById(R.id.text);
     buttonChangeTextSize = (Button)findViewById(R.id.changetextsize);
     
     buttonChangeTextSize.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    //Change Text Size of TextView
    text.setTextSize(50); 
    //Change Text Size of Button
    buttonChangeTextSize.setTextSize(35);
   }});
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:id="@+id/text"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button
    android:id="@+id/changetextsize"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="Change Text Size"
    />
</LinearLayout>

使用 Java 代碼動態改變按鈕的大小

我們可以使用 Java 碼, 通過改變佈局參數(LayoutParams)來改變按鈕的大小.

實例:

package com.AndroidButtonSize;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;

public class AndroidButtonSizeActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        final Button button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View v) {
    // TODO Auto-generated method stub
    LayoutParams params = button.getLayoutParams();
       params.width = 300;
       params.height = 200;
       button.setLayoutParams(params);
   }});
    }
}

谷歌發佈 Android 3.2 SDK 工具

谷歌剛剛發佈新的 Android 3.2 SDK 工具, 為用戶和開發人員添加了一些新功能. 新平台 API Level 13 包括一些API的變化。

• 更廣泛的平板電腦優化
• 固定大小應用程序的 zoom 的兼容性
• SD 卡的媒體同步
• 支持擴展屏幕的API

谷歌還同時更新了 SDK Tools (r12), Eclipse 插件 (ADT 12) 以及 NDK (r6).

詳情:
http://android-developers.blogspot.com/2011/07/android-32-platform-and-updated-sdk.html

通過EXTRA_OUTPUT, 指定並顯示使用 ACTION_IMAGE_CAPTURE 拍攝的圖像

在本博客的舊文章"通過EXTRA_OUTPUT, 指定儲存圖像的路徑"中, 描述了如何指定儲存圖像的路徑, 但沒有描述如何顯示拍攝的圖像. 本文將描述如何在onActivityResult()通過 BitmapFactory 顯示拍攝的圖像.

package com.AndroidImageCapture;

import java.io.File;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class AndroidImageCaptureActivity extends Activity {
 
 ImageView imageiewImageCaptured;
 String strImage;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button buttonImageCapture = (Button)findViewById(R.id.captureimage);
        imageiewImageCaptured = (ImageView)findViewById(R.id.imagecaptured);
        
        buttonImageCapture.setOnClickListener(buttonImageCaptureOnClickListener);
    }
    
    Button.OnClickListener buttonImageCaptureOnClickListener
    = new Button.OnClickListener(){

  public void onClick(View v) {
   // TODO Auto-generated method stub
   //Specify the path of the captured image
    strImage = Environment.getExternalStorageDirectory().getAbsolutePath()+"/mypicture.jpg";
    File myImage = new File(strImage);
    Uri uriMyImage = Uri.fromFile(myImage);
     
    Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
    intent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, uriMyImage);
    startActivityForResult(intent, 0);
  }
   };

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  // TODO Auto-generated method stub
  super.onActivityResult(requestCode, resultCode, data);
  if (resultCode == RESULT_OK)
  {
   Bitmap bmp = BitmapFactory.decodeFile(strImage);
   imageiewImageCaptured.setImageBitmap(bmp);
  }
 }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button
   android:id="@+id/captureimage"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Call for ACTION_IMAGE_CAPTURE"
   />
<ImageView
   android:id="@+id/imagecaptured"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   />
</LinearLayout>

如何鎖定屏幕方向, setRequestedOrientation

我們可以調用 getResources().getConfiguration().orientation 獲得當前的屏幕方向, 然後調用 setRequestedOrientation() 方法鎖定屏幕方向.

例子:

package com.AndroidFixOrientation;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;

public class AndroidFixOrientationActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        CheckBox fixOrientation = (CheckBox)findViewById(R.id.FixOrientation);
        
        fixOrientation.setOnCheckedChangeListener(new OnCheckedChangeListener(){

         int currentOrientation = getResources().getConfiguration().orientation;
         
   public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
    // TODO Auto-generated method stub
    if(arg1){
     switch(currentOrientation) {
      case Configuration.ORIENTATION_LANDSCAPE:
       setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
       break; 
      case Configuration.ORIENTATION_PORTRAIT:
       setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
       break;
      default:
       setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);  
     }
    }else{
     setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
    }
   }});
        

    }
}

檢索字符串資源, getString()

有時，我們將定義我們的字符串形式的資源

我們會使用資源(resources)的方式定義我們的字符串; 例如 /res/values/strings.xml 中的 "app_name".

如果我們要檢索這樣的字符串資源, 不能直接使用 myAppName = R.string.app_name, 我們要通過 getString() 方法檢索字符串資源.

例子:

package com.StringResource;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class StringResourceActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        TextView text1 = (TextView)findViewById(R.id.text1);
        TextView text2 = (TextView)findViewById(R.id.text2);
        
        text1.setText(R.string.app_name);
        
        String myAppName;
        //myAppName = R.string.app_name; //Error!
        myAppName = getString(R.string.app_name);
        text2.setText(myAppName);
    }
}