字母索引查詢ListView元件

現在很多Android應用都做了類似IOS的字母索引查詢功能，今天我將這個功能封裝成了一個元件

當點選或者在字母上上下移動時的畫面

package com.alphabet.widget;


import android.content.Context;
import android.graphics.Color;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;


/**
 * 右邊帶有字母查詢的ListView
 * @author Davee
 */
public class AlphabetListView extends FrameLayout {
    private Context mContext;


    private ListView mListView;
    private LinearLayout alphabetLayout;
    private TextView mTextView;


    private AlphabetPositionListener positionListener;
    
    private float screenDensity;
    
    private Handler mHandler;
    private HideIndicator mHideIndicator = new HideIndicator();
    
    private int indicatorDuration = 1000;
    public void setIndicatorDuration(int duration) {
        this.indicatorDuration = duration;
    }
    
    private final class HideIndicator implements Runnable {
        @Override
        public void run() {
            mTextView.setVisibility(View.INVISIBLE);
        }
    }


    public AlphabetListView(Context context) {
        super(context);
        init(context);
    }
    
    public AlphabetListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }
    
    private void init(Context context) {
        mContext = context;


        screenDensity = context.getResources().getDisplayMetrics().density;
        
        mHandler = new Handler();


        mListView = new ListView(mContext);


        initAlphabetLayout(mContext);


        mTextView = new TextView(mContext);
        mTextView.setTextSize(convertDIP2PX(50));
        mTextView.setTextColor(Color.argb(150, 255, 255, 255));
        mTextView.setBackgroundColor(Color.argb(200, 0, 0, 0));
        mTextView.setMinWidth(convertDIP2PX(70));
        mTextView.setMinHeight(convertDIP2PX(70));
        int pixels = convertDIP2PX(10);
        mTextView.setPadding(pixels, pixels, pixels, pixels);
        mTextView.setGravity(Gravity.CENTER);
        mTextView.setVisibility(View.INVISIBLE);
        FrameLayout.LayoutParams textLayoutParams = new FrameLayout.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT);
        textLayoutParams.gravity = Gravity.CENTER;
//        textLayoutParams.rightMargin = convertDIP2PX(10);
        mTextView.setLayoutParams(textLayoutParams);
    }
    
    public void setAdapter(ListAdapter adapter, AlphabetPositionListener positionListener) {
        if (positionListener == null) 
            throw new IllegalArgumentException("AlphabetPositionListener is required");


        mListView.setAdapter(adapter);


        this.positionListener = positionListener;


        this.addView(mListView);
        this.addView(alphabetLayout);
        this.addView(mTextView);
    }


    private void initAlphabetLayout(Context context) {
        //建立字母佈局
        alphabetLayout = new LinearLayout(context);
        alphabetLayout.setOrientation(LinearLayout.VERTICAL);
        FrameLayout.LayoutParams alphabetLayoutParams = new FrameLayout.LayoutParams(
                convertDIP2PX(30),
                ViewGroup.LayoutParams.FILL_PARENT);
        alphabetLayoutParams.gravity = Gravity.RIGHT|Gravity.CENTER_VERTICAL;
        alphabetLayoutParams.rightMargin = convertDIP2PX(10);
        alphabetLayout.setLayoutParams(alphabetLayoutParams);
        
        final String[] alphabet = new String[]{"A","B","C","D","E","F","G","H","I","J"
                ,"K","L","M","N","O","P","Q","L","S","T","U","V","W","X","Y","Z"};
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.WRAP_CONTENT
                ,LinearLayout.LayoutParams.WRAP_CONTENT);
        params.weight = 1;
        params.gravity = Gravity.CENTER_HORIZONTAL;
        for (int i=0, count=alphabet.length; i < count; i++) {
            TextView textView = new TextView(context);
            textView.setTextColor(Color.argb(150, 150, 150, 150));
            textView.setTextSize(convertDIP2PX(10));
            textView.setText(alphabet[i]);
            textView.setGravity(Gravity.CENTER);
            textView.setLayoutParams(params);
            textView.setTag(i+1);
            alphabetLayout.addView(textView);
        }
        alphabetLayout.setOnTouchListener(new OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch(event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        alphabetLayout.setBackgroundColor(Color.argb(50, 100, 200, 100));
                        int l = (int)(event.getY()/(alphabetLayout.getHeight()/26));
                        if (l > 25) l = 25;
                        else if (l < 0) l = 0;
                        int pos = positionListener.getPosition(alphabet[l]);
                        if (pos != -1) {
                            mTextView.setText(alphabet[l]);
                            mTextView.setVisibility(View.VISIBLE);
                            mHandler.removeCallbacks(mHideIndicator);
                            mHandler.postDelayed(mHideIndicator, indicatorDuration);
                            //mListView.requestFocusFromTouch();
                            mListView.setSelection(pos);
                        }
                        break;
                    case MotionEvent.ACTION_MOVE:
                        l = (int)((event.getY()+alphabetLayout.getHeight()/26/2)/(alphabetLayout.getHeight()/26));
                        if (l > 25) l = 25;
                        else if (l < 0) l = 0;
                        pos = positionListener.getPosition(alphabet[l]);
                        if (pos != -1) {
                            mTextView.setText(alphabet[l]);
                            mTextView.setVisibility(View.VISIBLE);
                            mHandler.removeCallbacks(mHideIndicator);
                            mHandler.postDelayed(mHideIndicator, indicatorDuration);
                            //mListView.requestFocusFromTouch();
                            mListView.setSelection(pos);
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                        alphabetLayout.setBackgroundResource(0);
                        break;
                }
                return true;
            }
        });
    }


    public int convertDIP2PX(float dip) {
        return (int)(dip*screenDensity + 0.5f*(dip>=0?1:-1));
    }
    
    public static interface AlphabetPositionListener {
        public static final int UNKNOW = -1;
        public int getPosition(String letter);
    }
}