Android开发之自定义View专题（一）：自定义柱形图

博主之前做的项目中，需要用到报表功能，之前在网上百度谷歌各种结果，没有一个是能够满足博主的老板的需求的，无奈之前博主只好自己去研究。终于研究出了一个不错的结果。先上效果图：

这是博主的一个项目的一个报表。老板要求可以点击左侧的月份进行月份比较，也可以点击选择月份，右边柱形图条状是可以响应点击事件的，并且可以左右滑动切换月份，如果柱形图内容过长超出界面，也是可以左右滑动查看未显示全的内容的。这里只讲柱形图的生成，其他界面效果博主就不讲解了。实际效果和这样有点差异，但不大，主要是实际效果在柱形图的顶端都还会显示数值。

自定义柱形图提供两种定义方式，可以在XML文件中写入，也可以再代码中new出来后加入一个容器中。这里博主就不在详细描述了，博主花了1个多小时才将该view从项目中独立出来。有兴趣的同学可以下载完整的项目下来学习。

github下载地址：https://github.com/victorfreedom1989/FreedomHistogram

CSDN下载地址：http://download.csdn.net/detail/victorfreedom/8309505

1、自定义柱形图第一步，自定义柱形条：

package com.freedom.histogram;

import java.text.DecimalFormat;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;

/**
 * @ClassName: FreedomHistogram
 * @author victor_freedom ([email protected])
 * @createddate 2014-12-28 下午10:44:52
 * @Description:
 */
public class FreedomHistogram {

	// 柱形条宽度
	private int with;
	// 柱形条高度
	private int height;
	// 柱形条对应数值
	private double count;
	// 起始Y坐标
	private int axisY;
	// 标题起始Y坐标
	private int titleY;

	// 柱形条起始X坐标
	private int axisX;
	private Context context;
	private DecimalFormat df;
	private Paint mPaint;

	public FreedomHistogram(Context context, int with, float axisY) {
		this.with = with;
		this.axisY = ScreenUtil.dip2px(context, axisY);
		this.titleY = ScreenUtil.dip2px(context, axisY + 35);
		this.context = context;
		this.df = new DecimalFormat("#0.0");
		mPaint = new Paint();
		mPaint.setAntiAlias(true);
		mPaint.setColor(Color.WHITE);
	}

	public FreedomHistogram() {
	};

	public int getAxisX() {
		return axisX;
	}

	public void setAxisX(int axisX) {
		this.axisX = axisX;
	}

	public int getHeight() {
		return height;
	}

	public void setHeight(int height) {
		this.height = height;
	}

	public double getCount() {
		return count;
	}

	public void setCount(double count) {
		this.count = count;
	}

	public void drawHistogram(Canvas canvas, Paint paint) {
		// 绘制第一层
		canvas.drawRect(axisX - 1, axisY - height - 1, with + axisX + 1, axisY,
				mPaint);
		// 绘制第二层，让柱形条有白边，好看，根据个人喜好可以不绘制第二层。
		canvas.drawRect(axisX, axisY - height, with + axisX, axisY - 1, paint);
		// 绘制柱形条对应的数值
		canvas.drawText(df.format(count),
				axisX - ScreenUtil.dip2px(context, 5), axisY - height - 10,
				paint);
	}

	public void drawTitle(Canvas canvas, Paint paint, String name) {
		// 绘制标题
		canvas.drawRect(axisX, titleY - height, with + axisX, titleY - 1, paint);
		canvas.drawText(name, with + axisX + ScreenUtil.dip2px(context, 5),
				titleY - 1, paint);
	}

}

2、自定义柱形图第二步：构建柱形图

package com.freedom.histogram;

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

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.DashPathEffect;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.PathEffect;
import android.graphics.PointF;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;

/**
 * @ClassName: FreedomHistogramView
 * @author victor_freedom ([email protected])
 * @createddate 2014-12-28 下午10:47:33
 * @Description: TODO
 */
public class FreedomHistogramView extends View {

	private HistogramOnClickListener histogramOnClickListener;

	public void setHistogramOnClickListener(HistogramOnClickListener listner) {
		this.histogramOnClickListener = listner;
	}

	// 柱形图总数据
	private Map<Integer, Double[]> datas;
	// 柱形图每一组数据
	private Double[] perData;
	// 最大值
	private double max;
	// 平局值
	private Double average;
	// 数据有多少组集合
	private ArrayList<Integer> dataKeys;
	// 每组数据的集合
	private ArrayList<Double[]> valuese;
	// 每组数据对应的区域
	private ArrayList<Rect> rects;
	// 数据有多少组
	private int flag;
	// 平均线数值
	private double avergerLine;

	// 每组数据对应的颜色
	private int[] colors = new int[] { 0xff8B008B, 0xff00BFFF, 0xff4800FF,
			0xff333333, 0xff006400, 0xff668B8B, 0xffFF83FA, 0xff363636,
			0xff000080, 0xff008B8B, 0xffFFDAB9, 0xff90EE90 };

	// 柱形图标题对应相距值
	private int margin;

	// 柱形条
	private FreedomHistogram freedomHistogram;
	private Paint paint;
	// 是否左下角绘制标题
	private boolean isTitle = false;
	private String title[];
	// 每组数据柱形条对应的X轴坐标说明
	private List<String> nodes;
	// 柱形条宽度
	private int charWith;
	// 柱形条间距（配合margin使用）
	private int withX;
	// Y周对应坐标点的个数
	private int numberY;
	// Y轴各坐标点之间的距离
	private float withY;

	public FreedomHistogramView(Context context, AttributeSet attrs,
			int defStyle) {
		super(context, attrs, defStyle);
	}

	/**
	 * Title: Description：在XML文件中的构建方法
	 *
	 * @param context
	 * @param attrs
	 */
	public FreedomHistogramView(Context context, AttributeSet attrs) {
		super(context, attrs);

		TypedArray a = context.obtainStyledAttributes(attrs,
				R.styleable.FreedomHistogramView);
		charWith = a.getInteger(R.styleable.FreedomHistogramView_charWith, 20);
		withX = a.getInteger(R.styleable.FreedomHistogramView_withX, 20);
		numberY = a.getInteger(R.styleable.FreedomHistogramView_numberY, 10);
		withY = a.getFloat(R.styleable.FreedomHistogramView_withY, 20);
		isTitle = a.getBoolean(R.styleable.FreedomHistogramView_isTitle, false);
		paint = new Paint();
		paint.setAntiAlias(true);
		// xPaint.setAntiAlias(true);
		// 新建一个柱形条
		freedomHistogram = new FreedomHistogram(context, ScreenUtil.dip2px(
				context, charWith), withY * (numberY - 1) + 10);
		a.recycle();
	}

	public FreedomHistogramView(Context context) {
		super(context);
	}

	public FreedomHistogramView(Context context, Map<Integer, Double[]> datas,
			int charWith, int withX, List<String> nodes, int numberY,
			float withY, boolean isTitle) {
		super(context);
		margin = 0;
		this.datas = datas;
		this.withX = withX;
		this.nodes = nodes;
		this.numberY = numberY;
		this.withY = withY;
		this.charWith = charWith;
		this.isTitle = isTitle;
		paint = new Paint();
		paint.setAntiAlias(true);
		// xPaint.setAntiAlias(true);
		// 新建一个柱形条
		freedomHistogram = new FreedomHistogram(context, ScreenUtil.dip2px(
				context, charWith), withY * (numberY - 1) + 10);

	}

	public Map<Integer, Double[]> getDatas() {
		return datas;
	}

	public String[] getTitle() {
		return title;
	}

	public void setTitle(String[] title) {
		this.title = title;
	}

	public void setDatas(Map<Integer, Double[]> datas) {
		this.datas = datas;
		// invalidate();
	}

	public boolean isTitle() {
		return isTitle;
	}

	public void setTitle(boolean isTitle) {
		this.isTitle = isTitle;
	}

	public List<String> getNodes() {
		return nodes;
	}

	public void setNodes(List<String> nodes) {
		this.nodes = nodes;
		// invalidate();
	}

	public int getCharWith() {
		return charWith;
	}

	public void setCharWith(int charWith) {
		this.charWith = charWith;
	}

	public int getwithX() {
		return withX;
	}

	public void setwithX(int withX) {
		this.withX = withX;
	}

	public float getNumberY() {
		return numberY;
	}

	public void setNumberY(int numberY) {
		this.numberY = numberY;
	}

	public float getWithY() {
		return withY;
	}

	public void setWithY(float withY) {
		this.withY = withY;
	}

	public void iniData() {
		// 取出数值
		Integer k;
		Double[] v;
		dataKeys = new ArrayList<Integer>();
		valuese = new ArrayList<Double[]>();
		for (Map.Entry<Integer, Double[]> entry : datas.entrySet()) {
			k = entry.getKey(); // key
			dataKeys.add(k);
			v = entry.getValue(); // value
			valuese.add(v);
		}
		this.flag = dataKeys.size();
		double total = 0;
		int sum = 0;
		for (Double[] dataMax : valuese) {
			max = dataMax[0];

			for (double data : dataMax) {
				total += data;
				max = max > data ? max : data;

				if (data != 0.0) {
					sum++;
				}
			}
		}
		max = dataChange(max);
		average = max / (numberY - 1);
		avergerLine = total / sum;
	}

	private double dataChange(double data) {
		StringBuilder sb = new StringBuilder();
		String dataString = String.valueOf(data);
		String dateInt = dataString.substring(0, dataString.lastIndexOf("."));
		int length = dateInt.length();
		String newDatafirst = dataString.substring(0, 1);
		if (newDatafirst.equals("9")) {
			boolean isChange = false;
			for (int i = 1; i < dataString.length(); i++) {
				String dataPer = dataString.substring(i, i + 1);
				if (dataPer.equals("0")) {
					continue;
				} else {
					isChange = true;
				}
			}
			if (isChange) {
				sb.append("1");
				for (int i = 0; i < length; i++) {
					sb.append("0");
				}
				return Double.valueOf(sb.toString());
			} else {
				return data;
			}
		} else {
			boolean isChange = false;
			for (int i = 1; i < dataString.length(); i++) {
				String dataPer = dataString.substring(i, i + 1);
				if (dataPer.equals("0")) {
					continue;
				} else {
					isChange = true;
					break;
				}
			}
			if (isChange) {
				newDatafirst = (Integer.valueOf(newDatafirst) + 1) + "";
				sb.append(newDatafirst);
				for (int i = 0; i < length - 1; i++) {
					sb.append("0");
				}
				return Double.valueOf(sb.toString());
			} else {
				return data;
			}

		}
	}

	public void drawAxis(Canvas canvas) {
		paint.setColor(Color.DKGRAY);
		paint.setStrokeWidth(ScreenUtil.dip2px(getContext(), 2));
		paint.setTextSize(ScreenUtil.sp2px(getContext(), 10));
		canvas.drawLine(
				ScreenUtil.dip2px(getContext(), 50),
				ScreenUtil.dip2px(getContext(), withY * (numberY - 1) + 10),
				ScreenUtil.dip2px(getContext(), (withX + (flag - 1) * charWith)
						* (nodes.size() + 1)),
				ScreenUtil.dip2px(getContext(), withY * (numberY - 1) + 10),
				paint);
		canvas.drawLine(ScreenUtil.dip2px(getContext(), 51),
				ScreenUtil.dip2px(getContext(), 5),
				ScreenUtil.dip2px(getContext(), 51),
				ScreenUtil.dip2px(getContext(), withY * (numberY - 1) + 10),
				paint);

		int x = ScreenUtil.dip2px(getContext(), (float) (59 + flag * charWith
				/ 2));
		int y = ScreenUtil.dip2px(getContext(), withY * (numberY - 1) + 10);

		for (int i = 0; i < nodes.size(); i++) {
			canvas.drawText(
					nodes.get(i),
					x,
					ScreenUtil.dip2px(getContext(), withY * (numberY - 1) + 25),
					paint);
			x += ScreenUtil.dip2px(getContext(), withX + (flag - 1) * charWith);
		}

		for (int i = 0; i < numberY; i++) {
			canvas.drawText(average.intValue() * i + "",
					ScreenUtil.dip2px(getContext(), 3), y, paint);
			y -= ScreenUtil.dip2px(getContext(), withY);
		}
	}

	public void drawChart(Canvas canvas) {
		rects = new ArrayList<Rect>();
		rects.clear();
		paint.setTextSize(ScreenUtil.sp2px(getContext(), 8));
		for (int j = 0; j < flag; j++) {
			paint.setColor(colors[j]);
			// paint.setStyle(Style.FILL_AND_STROKE);
			// paint.setStrokeWidth(1);
			perData = valuese.get(j);
			int temp_screen = ScreenUtil
					.dip2px(getContext(), 60 + j * charWith);
			for (int i = 0; i < perData.length; i++) {
				freedomHistogram.setCount(perData[i]);
				freedomHistogram.setHeight(ScreenUtil.dip2px(getContext(),
						(int) (perData[i].intValue() / max * (withY
								* (numberY - 1) + 10))));
				if (margin == 0) {
					freedomHistogram.setAxisX(temp_screen);
				} else {
					temp_screen += ScreenUtil.dip2px(getContext(), withX
							+ (flag - 1) * charWith);
					freedomHistogram.setAxisX(temp_screen);

				}
				freedomHistogram.drawHistogram(canvas, paint);
				margin = ScreenUtil.dip2px(getContext(), 10);
				Rect r = new Rect(temp_screen
						- ScreenUtil.dip2px(getContext(),
								(withX - charWith) / 3),
						ScreenUtil.dip2px(getContext(), withY * (numberY - 1))
								- ScreenUtil.dip2px(getContext(),
										(int) (perData[i].intValue() / max
												* withY * (numberY - 1))),
						temp_screen
								+ ScreenUtil.dip2px(getContext(), charWith)
								+ ScreenUtil.dip2px(getContext(),
										(withX - charWith) / 3),
						ScreenUtil.dip2px(getContext(), withY * (numberY - 1)));
				rects.add(r);
			}
			margin = 0;
		}

	}

	public void drawline(Canvas canvas) {
		// 虚线
		// Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
		Paint xPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
		xPaint.setAntiAlias(true);
		xPaint.setStyle(Style.STROKE);
		xPaint.setColor(Color.RED);
		xPaint.setStrokeWidth(2);
		PathEffect effects = new DashPathEffect(new float[] {
				ScreenUtil.dip2px(getContext(), 5),
				ScreenUtil.dip2px(getContext(), 5),
				ScreenUtil.dip2px(getContext(), 5),
				ScreenUtil.dip2px(getContext(), 5) }, 1);
		xPaint.setPathEffect(effects);
		canvas.drawLine(ScreenUtil.dip2px(getContext(), 51), ScreenUtil
				.dip2px(getContext(),
						withY
								* (numberY - 1)
								+ 10
								- (int) (avergerLine / max * (withY
										* (numberY - 1) + 10))), ScreenUtil
				.dip2px(getContext(),
						(withX + (flag - 1) * charWith) * (nodes.size() + 1)),
				ScreenUtil.dip2px(getContext(),
						withY
								* (numberY - 1)
								+ 10
								- (int) (avergerLine / max * (withY
										* (numberY - 1) + 10))), xPaint);
	}

	public void drawtitle(Canvas canvas) {
		paint.setTextSize(ScreenUtil.sp2px(getContext(), 12));
		int title_screen = ScreenUtil.dip2px(getContext(), charWith);

		for (int i = 0; i < dataKeys.size(); i++) {
			paint.setColor(colors[i]);
			freedomHistogram.setHeight(ScreenUtil.dip2px(getContext(), 10));
			if (margin == 0) {
				freedomHistogram.setAxisX(title_screen
						+ ScreenUtil.dip2px(getContext(), 30) + margin);
			} else {
				freedomHistogram.setAxisX(title_screen
						+ ScreenUtil.dip2px(getContext(), 40) + margin);

			}
			freedomHistogram.drawTitle(canvas, paint, title[i]);
			margin = ScreenUtil.dip2px(getContext(), 10);
			title_screen = freedomHistogram.getAxisX();
		}
		margin = 0;

	}

	/**
	 * 需要得到控件的宽和高
	 */
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		// 设置开关的宽和高为背景图片的宽高
		setMeasuredDimension(
				ScreenUtil.dip2px(getContext(), 60 + (withX + flag * charWith)
						* (nodes.size() + 1)),
				ScreenUtil.dip2px(getContext(), withY * numberY + 50));
	}

	@Override
	public void onDraw(Canvas canvas) {
		canvas.drawColor(Color.TRANSPARENT);
		iniData();
		drawChart(canvas);
		drawAxis(canvas);
		if (flag == 1) {
			drawline(canvas);
		}
		if (isTitle) {
			drawtitle(canvas);
		}
		super.onDraw(canvas);
	}

	private float scale;
	private float lastScale;
	private boolean firstTouch = true;
	private boolean guide = true;
	private boolean move = false;
	private int mode = 0;
	private int DRAG = 1;
	private int ZOOM = 2;
	private float startDis;
	int x1 = 0;
	int y1 = 0;
	private int startX = 0;

	@Override
	public boolean onTouchEvent(MotionEvent event) {

		switch (event.getAction() & MotionEvent.ACTION_MASK) {
		case MotionEvent.ACTION_DOWN:
			mode = DRAG;
			startX = (int) event.getRawX();
			scale = this.getScaleX();
			move = false;
			break;
		case MotionEvent.ACTION_MOVE:
			if (mode == DRAG) {
				int newX = (int) event.getRawX();
				int dx = newX - startX;
				if (dx > 10) {
					move = true;
				}
				int l = this.getLeft() + dx;
				int t = this.getTop();
				int r = this.getRight() + dx;
				int b = this.getBottom();
				this.layout(l, t, r, b);
				startX = (int) event.getRawX();
			} else if (mode == ZOOM) {
				float endDis = distance(event);
				if (endDis > 10f) {
					lastScale = scale;
					scale = endDis / startDis;
					if (firstTouch) {
						if (scale > lastScale) {
							guide = true;
						} else {
							guide = false;
						}
						firstTouch = false;
					}
					if (guide) {
						if (scale < lastScale) {
							scale = lastScale;
						}

					} else {
						if (scale > lastScale) {
							scale = lastScale;
						}
						scale = scale * lastScale;
						if (scale < 1) {
							lastScale = 1;
							scale = 1;
						}
					}

				}
			}
			break;
		case MotionEvent.ACTION_UP:

			if (scale == 1 && dataKeys.size() == 1 && !move) {
				x1 = (int) event.getX();
				y1 = (int) event.getY();
				getPosition(x1, y1);
			}
			break;
		// 当屏幕上已经有一个触点了，再有一个手指按下屏幕，就会相应
		case MotionEvent.ACTION_POINTER_DOWN:
			mode = ZOOM;
			firstTouch = true;
			move = true;
			startDis = distance(event);
			if (startDis > 10f) {
				// midPoint = mid(event);
			}
			break;

		// 手指离开屏幕，当屏幕还有一个手指在屏幕上时，就相应
		case MotionEvent.ACTION_POINTER_UP:
			mode = 0;
			break;

		}
		if (mode == ZOOM) {
			if (scale > 2) {
				lastScale = 2;
				scale = 2;
			}
			this.setScaleX(scale);

			if (scale == 1) {
				int l = 0;
				int t = 0;
				int r = this.getWidth();
				int b = this.getHeight();
				this.layout(l, t, r, b);
			}
		}
		return true;
	}

	private void getPosition(int x12, int y12) {

		if (null == rects) {
			return;
		}

		for (int i = 1; i <= rects.size(); i++) {
			Rect r = rects.get(i - 1);
			if (r.contains(x12, y12)) {
				if (null != histogramOnClickListener) {
					histogramOnClickListener.onClick(i);
				}

			}
		}

	}

	@SuppressLint("FloatMath")
	public float distance(MotionEvent event) {
		float dx = event.getX(1) - event.getX(0);
		float dy = event.getY(1) - event.getY(0);
		float dz = FloatMath.sqrt(dx * dx + dy * dy);

		return dz;
	}

	private PointF mid(MotionEvent event) {
		float dx = event.getX(1) + event.getX(0);
		float dy = event.getY(1) + event.getY(0);
		return new PointF(dx / 2, dy / 2);
	}

}
时间： 2024-08-10 19:16:51

Android开发之自定义View专题（一）：自定义柱形图的相关文章

Android开发之自定义View专题（三）：自定义GridView

gridview作为android开发中常用的组件,其功能十分强大.但是,我们有时候有很多特殊的需求,需要在其基础上进行改造.有时候会有移动gridView中item位置的需求,这个网上已经有很多例子,博主就不在描述.今天博主讲的是移动gridView中item中的内容.博主没看过网上那些移动item位置的demo,不知道其原理是不是和博主想的一样.博主思考过,似乎博主的这种实现原理似乎也可以用作实现移动item位置.而之前博主百思不得其解的小米手机的桌面的自定义乱序排放,似乎也可以用这个原理去

Android开发之自定义View专题（二）：自定义饼图

在图表里面,常用的图标一般为折线图.柱形图和饼图,上周,博主已经将柱形图分享.在博主的项目里面其实还用到了饼图,但没用到折线图.其实学会了其中一个,再去写其他的,应该都是知道该怎么写的,原理都是自己绘制图形,然后获取触摸位置判定点击事件.好了,废话不多说,直接上今天的饼图的效果图 这次也是博主从项目里面抽离出来的,这次的代码注释会比上次的柱形图更加的详细,更加便于有兴趣的朋友一起学习.图中的那个圆形指向箭头不属于饼图的部分,是在布局文件中为了美化另外添加进去的,有兴趣的朋友可以下载完整的项目下来

Android开发之自定义View专题（四）：自定义ViewGroup

有时候,我们会有这样的需求,一个activity里面需要有两个或者多个界面切换,就像Viewpager那样.但是在这些界面里面又需要能够有listView,gridview等组件.如果是纵向的,似乎还好,没什么影响,那么如果是横向的,那么就会出事情.因为Viewpager会拦截触摸事件.而如果将Viewpager的触摸事件拦截掉给里面的子控件,那么Viewpager又不能响应滑动事件了.那么如何又能让界面之间能够来回切换,又能让里面的子控件的触摸事件也能毫无影响的响应呢,这个时候,我们需要自定义

android开发最常用例子整理----(1)自定义按钮实现

android开发最常用例子整理----(1)自定义按钮实现 一.Activity MainActivity.java源码: public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } }

android开发最常用例子整理----(2)自定义ListView(SimpleAdapter实现)

android开发最常用例子整理----(2)自定义ListView(SimpleAdapter实现) 一.Activity MainActivity.java源码: public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layou

Android开发之图片处理专题（三）：利用ThreadPoolExcutor线程池实现多图片的异步加载

在上一篇专题Android开发之图片处理专题(二):利用AsyncTask和回调接口实现图片的异步加载和压缩中我们实现了listView的图片的大量加载.今天,我们换一种方式,采用线程池的方式来实现. 我们需要准备两个东西: 1.图片下载任务类 2.线程池. 1.图片下载任务类. 图片下载任务类,将需要显示的iamgeView,线程通讯消息管理者handler进行了封装.当图片下载无论成功还是失败,handler发送对应的消息,传入的iamgeView显示对应的图片.这里就不在应用软引用技术,采

Android开发之图片处理专题（二）：利用AsyncTask和回调接口实现图片的异步加载和压缩

在上一篇专题Android开发之图片处理专题(一):利用软引用构建图片高速缓存中我们讲述了如何利用软引用技术构建高速缓存.那么想要用到图片,首先得有图片的来源.一般而言,一个应用的图片资源都是从服务器处获得的.今天,我们利用Android开发之网络请求通信专题(二):基于HttpClient的文件上传下载里面封装好的httpUtils来实现图片的下载,然后加载到本地配合软引用缓存使用,以一个listView为例子来说明. 一.准备工作 我们需要准备以下几个类(图片对象和软引用缓存类请参考上一篇专

Android开发之图片处理专题（一）：利用软引用构建图片高速缓存

在Android开发中,图片处理是一个难点.对于大量的图片处理,一不小心就会出现OOM的错误.那么,构建缓存,就是非常必要的一个手段.利用软引用构建缓存,只是其中步骤之一,我们来看看一般情况下,图篇处理的流程. 一般而言,图片的处理流程大致如上,之前所说的Xutils的原理,也如此.今天,我们就先讲讲如何利用软引用技术来构建高速缓存. 一.对象的四种引用 在JDK 1.2以前的版本中,若一个对象不被任何变量引用,那么程序就无法再使用这个对象.也就是说,只有对象处于可触及(reachable)状态

Android开发学习之路--UI之自定义布局和控件

新的一年已经开始了,今天已经是初二了,两天没有学习了,还是要来继续学习下.一般手机的title都是actionbar,就像iphone一样可以后退,可以编辑.这里自定义布局就来实现下这个功能,首先准备下三张图片,一张用来当作背景,两张分别表示后退和编辑.新建工程UICostomViewsTest,然后自动创建工程后,新建title.xml,编写代码如下: <?xml version="1.0" encoding="utf-8"?> <LinearL