现在的位置: 首页 > 综合 > 正文

Android自定义控件实战——滚动选择器PickerView

2018年05月27日 ⁄ 综合 ⁄ 共 8814字 ⁄ 字号 评论关闭

   转载请声明出处http://blog.csdn.net/zhongkejingwang/article/details/38513301

  手机里设置闹钟需要选择时间,那个选择时间的控件就是滚动选择器,前几天用手机刷了MIUI,发现自带的那个时间选择器效果挺好看的,于是就自己仿写了一个,权当练手。先来看效果:

                                                                 

效果还行吧?实现思路就是自定义一个PickerView,单独滚动的是一个PickerView,显然上图中有分和秒的选择所以在布局里用了两个PickerView。由于这里不涉及到text的点击事件,所以只需要继承View就行了,直接把text用canvas画上去。PickerView的实现的主要难点:

难点1:

        字体随距离的渐变。可以看到,text随离中心位置的距离变化而变化,这里变化的是透明度alpha和字体大小TexSize,这两个值我都设置了Max和Min值,通过其与中心点的距离计算scale。我用的是变化曲线是抛物线scale=1-ax^2(x<=Height/4),scale = 0(x>Height/4),a=(4/Height)^2。x就是距离View中心的偏移量。用图片表示如下:


难点2:

     text的居中。绘制text的时候不仅要使其在x方向上居中,还要在y方向上居中,在x方向上比较简单,设置Paint的Align为Align.CENTER就行了,但是y方向上很蛋疼,需要计算text的baseline。

难点3:

    循环滚动。为了解决循环滚动的问题我把存放text的List从中间往上下摊开,通过不断地moveHeadToTail和moveTailToHead使选中的text始终是list的中间position的值。

  

     以上就是几个难点,了解了之后可以来看PickerView的代码了:

package com.jingchen.timerpicker;

import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Align;
import android.graphics.Paint.FontMetricsInt;
import android.graphics.Paint.Style;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * 滚动选择器
 * 
 * @author chenjing
 * 
 */
public class PickerView extends View
{

	public static final String TAG = "PickerView";
	/**
	 * text之间间距和minTextSize之比
	 */
	public static final float MARGIN_ALPHA = 2.8f;
	/**
	 * 自动回滚到中间的速度
	 */
	public static final float SPEED = 2;

	private List<String> mDataList;
	/**
	 * 选中的位置,这个位置是mDataList的中心位置,一直不变
	 */
	private int mCurrentSelected;
	private Paint mPaint;

	private float mMaxTextSize = 80;
	private float mMinTextSize = 40;

	private float mMaxTextAlpha = 255;
	private float mMinTextAlpha = 120;

	private int mColorText = 0x333333;

	private int mViewHeight;
	private int mViewWidth;

	private float mLastDownY;
	/**
	 * 滑动的距离
	 */
	private float mMoveLen = 0;
	private boolean isInit = false;
	private onSelectListener mSelectListener;
	private Timer timer;
	private MyTimerTask mTask;

	Handler updateHandler = new Handler()
	{

		@Override
		public void handleMessage(Message msg)
		{
			if (Math.abs(mMoveLen) < SPEED)
			{
				mMoveLen = 0;
				if (mTask != null)
				{
					mTask.cancel();
					mTask = null;
					performSelect();
				}
			} else
				// 这里mMoveLen / Math.abs(mMoveLen)是为了保有mMoveLen的正负号,以实现上滚或下滚
				mMoveLen = mMoveLen - mMoveLen / Math.abs(mMoveLen) * SPEED;
			invalidate();
		}

	};

	public PickerView(Context context)
	{
		super(context);
		init();
	}

	public PickerView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
		init();
	}

	public void setOnSelectListener(onSelectListener listener)
	{
		mSelectListener = listener;
	}

	private void performSelect()
	{
		if (mSelectListener != null)
			mSelectListener.onSelect(mDataList.get(mCurrentSelected));
	}

	public void setData(List<String> datas)
	{
		mDataList = datas;
		mCurrentSelected = datas.size() / 2;
		invalidate();
	}

	public void setSelected(int selected)
	{
		mCurrentSelected = selected;
	}

	private void moveHeadToTail()
	{
		String head = mDataList.get(0);
		mDataList.remove(0);
		mDataList.add(head);
	}

	private void moveTailToHead()
	{
		String tail = mDataList.get(mDataList.size() - 1);
		mDataList.remove(mDataList.size() - 1);
		mDataList.add(0, tail);
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
	{
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		mViewHeight = getMeasuredHeight();
		mViewWidth = getMeasuredWidth();
		// 按照View的高度计算字体大小
		mMaxTextSize = mViewHeight / 4.0f;
		mMinTextSize = mMaxTextSize / 2f;
		isInit = true;
		invalidate();
	}

	private void init()
	{
		timer = new Timer();
		mDataList = new ArrayList<String>();
		mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
		mPaint.setStyle(Style.FILL);
		mPaint.setTextAlign(Align.CENTER);
		mPaint.setColor(mColorText);
	}

	@Override
	protected void onDraw(Canvas canvas)
	{
		super.onDraw(canvas);
		// 根据index绘制view
		if (isInit)
			drawData(canvas);
	}

	private void drawData(Canvas canvas)
	{
		// 先绘制选中的text再往上往下绘制其余的text
		float scale = parabola(mViewHeight / 4.0f, mMoveLen);
		float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;
		mPaint.setTextSize(size);
		mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));
		// text居中绘制,注意baseline的计算才能达到居中,y值是text中心坐标
		float x = (float) (mViewWidth / 2.0);
		float y = (float) (mViewHeight / 2.0 + mMoveLen);
		FontMetricsInt fmi = mPaint.getFontMetricsInt();
		float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));

		canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);
		// 绘制上方data
		for (int i = 1; (mCurrentSelected - i) >= 0; i++)
		{
			drawOtherText(canvas, i, -1);
		}
		// 绘制下方data
		for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)
		{
			drawOtherText(canvas, i, 1);
		}

	}

	/**
	 * @param canvas
	 * @param position
	 *            距离mCurrentSelected的差值
	 * @param type
	 *            1表示向下绘制,-1表示向上绘制
	 */
	private void drawOtherText(Canvas canvas, int position, int type)
	{
		float d = (float) (MARGIN_ALPHA * mMinTextSize * position + type
				* mMoveLen);
		float scale = parabola(mViewHeight / 4.0f, d);
		float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;
		mPaint.setTextSize(size);
		mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));
		float y = (float) (mViewHeight / 2.0 + type * d);
		FontMetricsInt fmi = mPaint.getFontMetricsInt();
		float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));
		canvas.drawText(mDataList.get(mCurrentSelected + type * position),
				(float) (mViewWidth / 2.0), baseline, mPaint);
	}

	/**
	 * 抛物线
	 * 
	 * @param zero
	 *            零点坐标
	 * @param x
	 *            偏移量
	 * @return scale
	 */
	private float parabola(float zero, float x)
	{
		float f = (float) (1 - Math.pow(x / zero, 2));
		return f < 0 ? 0 : f;
	}

	@Override
	public boolean onTouchEvent(MotionEvent event)
	{
		switch (event.getActionMasked())
		{
		case MotionEvent.ACTION_DOWN:
			doDown(event);
			break;
		case MotionEvent.ACTION_MOVE:
			doMove(event);
			break;
		case MotionEvent.ACTION_UP:
			doUp(event);
			break;
		}
		return true;
	}

	private void doDown(MotionEvent event)
	{
		if (mTask != null)
		{
			mTask.cancel();
			mTask = null;
		}
		mLastDownY = event.getY();
	}

	private void doMove(MotionEvent event)
	{

		mMoveLen += (event.getY() - mLastDownY);

		if (mMoveLen > MARGIN_ALPHA * mMinTextSize / 2)
		{
			// 往下滑超过离开距离
			moveTailToHead();
			mMoveLen = mMoveLen - MARGIN_ALPHA * mMinTextSize;
		} else if (mMoveLen < -MARGIN_ALPHA * mMinTextSize / 2)
		{
			// 往上滑超过离开距离
			moveHeadToTail();
			mMoveLen = mMoveLen + MARGIN_ALPHA * mMinTextSize;
		}

		mLastDownY = event.getY();
		invalidate();
	}

	private void doUp(MotionEvent event)
	{
		// 抬起手后mCurrentSelected的位置由当前位置move到中间选中位置
		if (Math.abs(mMoveLen) < 0.0001)
		{
			mMoveLen = 0;
			return;
		}
		if (mTask != null)
		{
			mTask.cancel();
			mTask = null;
		}
		mTask = new MyTimerTask(updateHandler);
		timer.schedule(mTask, 0, 10);
	}

	class MyTimerTask extends TimerTask
	{
		Handler handler;

		public MyTimerTask(Handler handler)
		{
			this.handler = handler;
		}

		@Override
		public void run()
		{
			handler.sendMessage(handler.obtainMessage());
		}

	}

	public interface onSelectListener
	{
		void onSelect(String text);
	}
}


代码里的注释都写的很清楚了。接下来,我们就用写好的PickerView实现文章开头的图片效果吧~

首先看MainActivity的布局:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000" >

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:background="#ffffff" >

        <com.jingchen.timerpicker.PickerView
            android:id="@+id/minute_pv"
            android:layout_width="80dp"
            android:layout_height="160dp" />

        <TextView
            android:id="@+id/minute_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_toRightOf="@id/minute_pv"
            android:text="分"
            android:textColor="#ffaa33"
            android:textSize="26sp"
            android:textStyle="bold" />

        <com.jingchen.timerpicker.PickerView
            android:id="@+id/second_pv"
            android:layout_width="80dp"
            android:layout_height="160dp"
            android:layout_toRightOf="@id/minute_tv" />

        <TextView
            android:id="@+id/second_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_toRightOf="@id/second_pv"
            android:text="秒"
            android:textColor="#ffaa33"
            android:textSize="26sp"
            android:textStyle="bold" />
    </RelativeLayout>

</RelativeLayout>

两个PickerView两个TextView,很简单。

下面是MainActivity的代码:

package com.jingchen.timerpicker;

import java.util.ArrayList;
import java.util.List;

import com.jingchen.timerpicker.PickerView.onSelectListener;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity
{

	PickerView minute_pv;
	PickerView second_pv;

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		minute_pv = (PickerView) findViewById(R.id.minute_pv);
		second_pv = (PickerView) findViewById(R.id.second_pv);
		List<String> data = new ArrayList<String>();
		List<String> seconds = new ArrayList<String>();
		for (int i = 0; i < 10; i++)
		{
			data.add("0" + i);
		}
		for (int i = 0; i < 60; i++)
		{
			seconds.add(i < 10 ? "0" + i : "" + i);
		}
		minute_pv.setData(data);
		minute_pv.setOnSelectListener(new onSelectListener()
		{

			@Override
			public void onSelect(String text)
			{
				Toast.makeText(MainActivity.this, "选择了 " + text + " 分",
						Toast.LENGTH_SHORT).show();
			}
		});
		second_pv.setData(seconds);
		second_pv.setOnSelectListener(new onSelectListener()
		{

			@Override
			public void onSelect(String text)
			{
				Toast.makeText(MainActivity.this, "选择了 " + text + " 秒",
						Toast.LENGTH_SHORT).show();
			}
		});
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu)
	{
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

OK了,自定义自己的TimerPicker就是这么简单~

源码下载

抱歉!评论已关闭.