Android开发记录（7）-自定义百分比动态折线图

要求实现一个折线（曲线）图来查看android设备的内存和CPU占用情况。
场景主要用于设备测试和实时监控。

先看下实现效果

效果图.gif

这里用的是随机生成数据演示，当然实际上CPU和内存使用情况不会如此大幅度变化。

实现过程

一、自定义属性

自定义属性的好处主要体现在适配不同分辨率的设备，因为自定义View的绘画单位是px，而我们指定设置dp值转为px就能让视图在不同设备中展示出一样的效果。
在values目录下新建attrs.xml文件，自定义属性如下：

二、自定义view

直接上代码

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

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;

public class LineChartView extends View{
    private Paint paint;
    private float XPoint = 0;
    private float XScale = 0;
    private float YScale = 0;
    private float XLength = 0;
    private float YLength = 0;
    private float DEFAULT_XPoint = 50;
    private float DEFAULT_XScale = 8;
    private float DEFAULT_YScale = 60;
    private float DEFAULT_XLength = 320;
    private float DEFAULT_YLength = 300;
    private int MaxDataSize = 0 ;
    //内存数据
    private List dataMemory = new ArrayList();
    //CPU数据
    private List dataCPU = new ArrayList();
    //刻度
    private String[] YLabel = new String[]{"0","25","50","75","100"};

    private Handler handler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            // TODO Auto-generated method stub
            switch (msg.what) {
                case 1:
                LineChartView.this.invalidate();
            }
            return false;
        }
    });

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

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

    public LineChartView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initAttr(context, attrs);
        init();
    }

    /**
     * 获得属性值
     * @param context
     * @param attrs
     */
    private void initAttr(Context context, AttributeSet attrs) {
        if (attrs == null) {
            return;
        }
        TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.LineChartView);
        int n = array.getIndexCount();
        for (int i = 0; i < n; i++) {
            int attr = array.getIndex(i);
            if (attr == R.styleable.LineChartView_XPoint) {
                XPoint = array.getDimension(attr, dp2px(context, DEFAULT_XPoint));
            } else if (attr == R.styleable.LineChartView_XScale) {
                XScale = array.getDimension(attr, dp2px(context, DEFAULT_XScale));
            } else if (attr == R.styleable.LineChartView_YScale) {
                YScale = array.getDimension(attr, dp2px(context, DEFAULT_YScale));
            }else if (attr == R.styleable.LineChartView_XLength) {
                XLength = array.getDimension(attr, dp2px(context, DEFAULT_XLength));
            }else if (attr == R.styleable.LineChartView_YLength) {
                YLength = array.getDimension(attr, dp2px(context, DEFAULT_YLength));
            }
        }
        array.recycle();
    }

    private void init(){
        paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setAntiAlias(true);
        //刻度
        YLabel[0]="0";
        YLabel[1]="25";
        YLabel[2]="50";
        YLabel[3]="75";
        YLabel[4]="100";
        //计算最大数据数
        MaxDataSize = Math.round(XLength / XScale);
    }

    /**
     * 更新内存、CPU数据
     * @param newDataMemory
     * @param newDataCPU
     */
    public void setNewData(Float newDataMemory,Float newDataCPU){
        //memory
        if(dataMemory.size() >= MaxDataSize){
            dataMemory.remove(0);
        }
        dataMemory.add(newDataMemory);
        //cpu
        if(dataCPU.size() >= MaxDataSize){
            dataCPU.remove(0);
        }
        dataCPU.add(newDataCPU);
        //update
        handler.sendEmptyMessage(1);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        paint.setColor(Color.BLUE);
        //画Y轴
        canvas.drawLine(XPoint, 0, XPoint, YLength, paint);
        //Y轴箭头
        canvas.drawLine(XPoint, 0, XPoint - 3, 6, paint);  //箭头
        canvas.drawLine(XPoint, 0, XPoint + 3, 6 ,paint);
        //添加刻度和文字
        for(int i=0; i * YScale < YLength; i++) {
            canvas.drawLine(XPoint, YLength - i * YScale, XPoint + 5, YLength - i * YScale, paint);  //刻度
            canvas.drawText(YLabel[i], XPoint - 30, YLength - i * YScale, paint);//文字
        }
        //画X轴
        canvas.drawLine(XPoint, YLength, XPoint + XLength, YLength, paint);
        //画标识
        paint.setColor(Color.RED);
        canvas.drawText("内存百分比", XLength, 15, paint);//文字
        canvas.drawLine(XLength-20, 15, XLength-10, 15, paint);
        paint.setColor(Color.MAGENTA);
        canvas.drawText("CPU百分比", XLength, 30, paint);//文字
        canvas.drawLine(XLength-20, 30, XLength-10, 30, paint);

        //画内存数据
        paint.setColor(Color.RED);
        if(dataMemory.size() > 1){
            for(int i=1; i 1){
            for(int i=1; i

具体的注释应该还算清晰。

三、XML中使用

四、Activity中使用

请根据实际使用填充数据，这里只以演示效果2秒随机生成数值填充。如效果图所示。

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import com.components.LineChartView;

import butterknife.BindView;
import butterknife.ButterKnife;

public class TestActivity extends AppCompatActivity {
    @BindView(R.id.linechart)
    LineChartView linechart;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
        ButterKnife.bind(this);

        new Thread(){
            public void run(){
                while (true){
                    try {
                        Thread.sleep(2000);
                        linechart.setNewData((float)Math.random(),(float)Math.random());
                    }catch (InterruptedException e){
                        e.printStackTrace();
                    }
                }
            }
        }.start();
    }
}