Android拖動相片特效

你曾經被iphone用手指在螢幕劃來花去拖動相片吸引嗎？在Android同樣能夠實現，而且不是什麼難事。

這裡需要用到android.content.Context;android.widget.BaseAdapter;android.wiget.ImageView；等。

android.content.Context在Activity中類似於一張Canvas畫布，能夠隨時處理或覆蓋它。Context與Intent一樣是android.content的子類。

本執行個體通過在layout中放置Gallery對象，然後通過android.widget.BaseAdapter容器放置Gallery所需要的圖片，本案例使用系統預設的ICON圖片。

1.，拖拽Gallery控制項到layout中，ID設定為myGallery1

查看res/layout/main.xml

<?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"    >    <Gallery android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:id="@+id/myGallery1"></Gallery></LinearLayout>

src/EX03_15.java

package gphone.ex03_15;import android.app.Activity;import android.content.Context;import android.os.Bundle;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.Gallery;import android.widget.ImageView;public class EX03_15 extends Activity {private Gallery myGallery1=null;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                myGallery1=(Gallery)findViewById(R.id.myGallery1);        myGallery1.setAdapter(new ImageAdapter(this));    }    public class ImageAdapter extends BaseAdapter{    private Context myContext;    //使用android.R.drawable裡系統預設圖片作為圖片源    private int[] myImageIds={    android.R.drawable.btn_minus,    android.R.drawable.btn_radio,    android.R.drawable.ic_lock_idle_low_battery,    android.R.drawable.ic_menu_camera,    android.R.drawable.btn_minus,    android.R.drawable.btn_radio,    android.R.drawable.ic_lock_idle_low_battery,    android.R.drawable.ic_menu_camera,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;    }        @Override    public int getCount() {    // TODO Auto-generated method stub    return this.myImageIds.length;    }    @Override    public Object getItem(int position) {    // TODO Auto-generated method stub    return position;    }    @Override    public long getItemId(int position) {    // TODO Auto-generated method stub    return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {    // 建立ImageView    ImageView i=new ImageView(this.myContext);        i.setImageResource(this.myImageIds[position]);    i.setScaleType(ImageView.ScaleType.FIT_XY);    //設定ImageView對象的寬高，單位為dip    i.setLayoutParams(new Gallery.LayoutParams(120, 120));        return i;    }    //根據中心點位移量 利用getScale返回views的大小（0.0f-1.0f）    public float getScale(boolean focused,int offset){    return Math.max(0,1.0f/(float)Math.pow(2,Math.abs(offset)));    }        }}

運行效果