Android开发-自定义View-AndroidStudio(十四)快速索引(1)

package com.iwanghang.indexeddemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements IndexView.WordListener {

    private TextView tv_main;

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

        tv_main = (TextView) findViewById(R.id.tv_main);
    }

    /**
     * 实现IndexView中的字母改变的接口
     */
    @Override
    public void wordListener(String word) {
        // 当触摸的字母发生改变，这里接到回传，重新设置TextView
        tv_main.setText(word);
    }
}

package com.iwanghang.indexeddemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * 绘制快速索引的字母
 */
public class IndexView extends View{

    private String[] words = {"A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z"};

    // 包裹字母的条目的宽高
    private int itemWidth;
    private int itemHeight;

    private String word;

    private int wordWidth;
    private int wordHeight;
    private float wordX;
    private float wordY;

    private Paint paint;

    public IndexView(Context context, AttributeSet attrs) {
        super(context, attrs);
        paint = new Paint();
        paint.setTextSize(25);
        paint.setColor(Color.WHITE);
        paint.setAntiAlias(true); // 抗锯齿，字体圆滑
        paint.setTypeface(Typeface.DEFAULT_BOLD);//设置粗体字
    }

    // 测量包裹字母的条目的宽高
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        itemWidth = getMeasuredWidth();
        itemHeight = getMeasuredHeight()/26;
    }

    // 在画布上 绘制字母
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        for (int i = 0; i < 26; i++) {

            // 根据onTouchEvent 监听手势滑动位置，设置当前滑动的字母的下标 来设置字母颜色 A2
            if(touchIndex == i){
                //设置灰色
                paint.setColor(Color.GRAY);
            }else{
                //设置白色
                paint.setColor(Color.WHITE);
            }

            word = words[i];

            Rect rect = new Rect();
            // 画笔
            // 0,1的取一个字母
            paint.getTextBounds(word, 0, 1, rect);

            // 字母的高和宽
            wordWidth = rect.width();
            wordHeight = rect.height();

            // 计算每个字母在视图上的坐标位置
            //wordX = itemWidth / 2 - wordWidth / 2;
            //wordY = itemHeight / 2 + wordHeight / 2 + i * itemHeight;

            wordX = itemWidth / 2 - wordWidth / 2;
            wordY = itemHeight / 2 + wordHeight / 2 + i * itemHeight;

            canvas.drawText(word, wordX, wordY, paint);
        }
    }

    // 字母的下标位置
    private int touchIndex = -1;

    /**
     * 监听手势滑动位置，设置当前滑动的字母的下标 A1
     */
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        super.onTouchEvent(event);
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                float Y = event.getY();
                int index = (int) (Y/itemHeight); // 字母索引
                if(index != touchIndex){
                    touchIndex = index;
                    invalidate(); // 强制绘制onDraw();
                }

                System.out.println(touchIndex);
                if (touchIndex > -1 && touchIndex < 26) {
                    WordListener listener = (WordListener) getContext(); // 回调接口 B2
                    listener.wordListener(words[touchIndex]); // 回传触摸的字母,告诉MainActivity
                }

                break;
            case MotionEvent.ACTION_UP:
                touchIndex = -1;
                invalidate();
                break;
        }
        return true; // 返回true，拦截事件分发
    }

    // 回调接口 B1
    public interface WordListener { // 下载是否成功.监听.按钮回调接口
        void wordListener(String word); // 回传一个字符串
    }

}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.iwanghang.indexeddemo.MainActivity">

    <ListView
        android:id="@+id/lv_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <TextView
        android:id="@+id/tv_main"
        android:layout_centerInParent="true"
        android:textSize="30sp"
        android:gravity="center"
        android:textColor="#FFFFFF"
        android:background="#44000000"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:text="A" />

    <com.iwanghang.indexeddemo.IndexView
        android:id="@+id/iv_words"
        android:layout_alignParentRight="true"
        android:background="#44000000"
        android:layout_width="30dp"
        android:layout_height="match_parent" />

</RelativeLayout>

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