一點(diǎn)感想

開發(fā)中, 其實(shí)經(jīng)常會(huì)碰到這種情況, 拿到一個(gè)文件幾百上千行的代碼, 到處是各種對framework的API調(diào)用, 如果對這些API調(diào)用的作用理解不清晰, 就會(huì)造成各種困擾, 不斷的去用google查排疑解惑, 打亂自己的思緒, 對理解整個(gè)的代碼邏輯造成不小的困擾. 相反, 如果對這些API調(diào)用的作用理解清晰的話, 那就能快速的找到代碼中的重點(diǎn)位置, 腦子里能快速想象出這段代碼要干的大體是什么事情, 這樣就能快速的理解透原來的代碼邏輯, 進(jìn)而添加自己要實(shí)現(xiàn)的功能.
而有些不常用的代碼,

        Shader mShader = new LinearGradient(0, 0, 100, 100, new int[]{
                Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW}, null,
                Shader.TileMode.MIRROR);
        paint.setShader(mShader);

像這樣的, 平時(shí)如果不進(jìn)行知識(shí)積累的話, 閱讀到這里就會(huì)卡下來, 生怕這是關(guān)鍵的代碼邏輯, 被自己遺漏掉, 思緒就會(huì)因此被打亂. 反過來說, 如果對framework 的API很熟悉, 那就能快速過濾"無用"代碼, 定位在代碼中的關(guān)鍵邏輯中.
所以說, 在工作之余, 一定要抽出些時(shí)間, 進(jìn)行知識(shí)上的積累, 對技術(shù)成長很有幫助.
在PC上建一個(gè)文件夾, 保存好各開發(fā)要點(diǎn)的代碼片段.

/home/wangxin/src/my_code_base

例子代碼

package net.qihoo.launcher.widget.clockweather.components;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PixelFormat;
import android.graphics.RectF;
import android.graphics.Shader;
import android.view.View;
import android.view.WindowManager;

/*
1. 外界的調(diào)用方法, 讓這個(gè)子定義view 直接添加到WindowManager中去.
        MyView myView = new MyView(mContext);
        myView.show();

要準(zhǔn)確理解幾個(gè)基本概念.
2. Canvas: 畫布, 任何圖形都是在畫布上畫出來的.
調(diào)用canvas.draw*() 系列方法, 在畫布上繪制幾何圖形.
3. Paint: 畫筆, 可以指定畫筆的顏色, 寬度等值, 調(diào)用canvas.draw*() 系列方法都需要傳入Paint類的對象進(jìn)去才行.
//作用是去鋸齒, 因?yàn)槠聊簧系膱D形都是由方形的像素組成, 如果不調(diào)用這個(gè)方法的話, 在繪制斜線的時(shí)候就會(huì)看到明顯的鋸齒情況出現(xiàn).
paint.setAntiAlias(true);

3. Path類, 描述的是一個(gè)繪制的路徑信息.
        Path path = new Path();
        path.moveTo(10, 330);
        path.lineTo(70, 330);
        path.lineTo(40, 270);
        path.close();
        canvas.drawPath(path, paint);
4. Shader類, 描述的是漸變顏色的信息.
    調(diào)用Paint的setShader(mShader);的目的是為這個(gè)畫筆設(shè)置漸變顏色.
        Shader mShader = new LinearGradient(0, 0, 100, 100, new int[]{
                Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW}, null,
                Shader.TileMode.MIRROR);
        paint.setShader(mShader);

*/


public class MyView extends View {

    WindowManager wm;
    private WindowManager.LayoutParams params;

    public MyView(Context context) {
        super(context);
        wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        params = new WindowManager.LayoutParams(WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.MATCH_PARENT,
                WindowManager.LayoutParams.TYPE_APPLICATION_PANEL,
                WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN /*| WindowManager.LayoutParams.FLAG_BLUR_BEHIND*/,
                PixelFormat.TRANSLUCENT);
        params.softInputMode = WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED | WindowManager.LayoutParams.SOFT_INPUT_ADJUST_PAN;
        params.windowAnimations = android.R.style.Animation_Dialog;
    }

    //會(huì)在組件加載時(shí)調(diào)用
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        /* 設(shè)置背景為白色 */
        canvas.drawColor(Color.WHITE);
        Paint paint = new Paint();//創(chuàng)建畫筆
        /* 去鋸齒 */
        paint.setAntiAlias(true);
        /* 設(shè)置paint的顏色 */
        paint.setColor(Color.RED);
        /* 設(shè)置paint的 style 為STROKE:空心 */
        paint.setStyle(Paint.Style.STROKE);
        /* 設(shè)置paint的外框?qū)挾?*/
        paint.setStrokeWidth(3);
        /* 畫一個(gè)空心圓形 */
        //參數(shù):圓心x,圓心y,半徑r,paint
        canvas.drawCircle(40, 40, 30, paint);
        /* 畫一個(gè)空心正方形 */
        //參數(shù):left top right bottom ,當(dāng)right-left等于bottom-top就為正方形 canvas.drawRect(10, 90, 70, 150, paint);
        /* 畫一個(gè)空心長方形 */
        canvas.drawRect(10, 170, 70, 200, paint);
        /* 畫一個(gè)空心橢圓形 */
        RectF re = new RectF(10, 220, 70, 250);
        canvas.drawOval(re, paint);

        /* 畫一個(gè)空心三角形 */
        Path path = new Path();
        path.moveTo(10, 330);
        path.lineTo(70, 330);
        path.lineTo(40, 270);
        path.close();
        canvas.drawPath(path, paint);
        /* 畫一個(gè)空心梯形 */
        Path path1 = new Path();
        path1.moveTo(10, 410);
        path1.lineTo(70, 410);
        path1.lineTo(55, 350);
        path1.lineTo(25, 350);
        path1.close();
        canvas.drawPath(path1, paint);
        /* 設(shè)置paint 的style為 FILL:實(shí)心 */
        paint.setStyle(Paint.Style.FILL);
        /* 設(shè)置paint的顏色 */
        paint.setColor(Color.BLUE);
        /* 畫一個(gè)實(shí)心圓 */
        canvas.drawCircle(120, 40, 30, paint);
        /* 畫一個(gè)實(shí)心正方形 */
        canvas.drawRect(90, 90, 150, 150, paint);
/* 畫一個(gè)實(shí)心長方形 */
        canvas.drawRect(90, 170, 150, 200, paint);
/* 畫一個(gè)實(shí)心橢圓 */
        RectF re2 = new RectF(90, 220, 150, 250);
        canvas.drawOval(re2, paint);
/* 畫一個(gè)實(shí)心三角形 */
        Path path2 = new Path();
        path2.moveTo(90, 330);
        path2.lineTo(150, 330);
        path2.lineTo(120, 270);
        path2.close();
        canvas.drawPath(path2, paint);
        /* 畫一個(gè)實(shí)心梯形 */
        Path path3 = new Path();
        path3.moveTo(90, 410);
        path3.lineTo(150, 410);
        path3.lineTo(135, 350);
        path3.lineTo(105, 350);
        path3.close();
        canvas.drawPath(path3, paint);
        /* 設(shè)置漸變色 */
        /*
        LinearGradient shader = new LinearGradient(0, 0, endX, endY, new int[]{startColor, midleColor, endColor},new float[]{0 , 0.5f, 1.0f}, TileMode.MIRROR);
        參數(shù)一為漸變起初點(diǎn)坐標(biāo)x位置,參數(shù)二為y軸位置,參數(shù)三和四分別對應(yīng)漸變終點(diǎn)
        其中參數(shù)new int[]{startColor, midleColor, endColor}是參與漸變效果的顏色集合,
        其中參數(shù)new float[]{0 , 0.5f, 1.0f}是定義每個(gè)顏色處于的漸變相對位置, 這個(gè)參數(shù)可以為null,如果為null表示所有的顏色按順序均勻的分布
        最后參數(shù)為平鋪方式,這里設(shè)置為MIRROR鏡像(REPEAT重復(fù))
        */
        Shader mShader = new LinearGradient(0, 0, 100, 100, new int[]{
                Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW}, null,
                Shader.TileMode.MIRROR);
        paint.setShader(mShader);
        /* 畫一個(gè)漸變色圓 */
        canvas.drawCircle(200, 40, 30, paint);
        /* 畫一個(gè)漸變色正方形 */
        canvas.drawRect(170, 90, 230, 150, paint);
        /* 畫一個(gè)漸變色長方形 */
        canvas.drawRect(170, 170, 230, 200, paint);
        /* 畫一個(gè)漸變色橢圓 */
        RectF re3 = new RectF(170, 220, 230, 250);
        canvas.drawOval(re3, paint);
        /* 畫一個(gè)漸變色三角形 */
        Path path4 = new Path();
        path4.moveTo(170, 330);
        path4.lineTo(230, 330);
        path4.lineTo(200, 270);
        path4.close();
        canvas.drawPath(path4, paint);
        /* 畫一個(gè)漸變色梯形 */
        Path path5 = new Path();
        path5.moveTo(170, 410);
        path5.lineTo(230, 410);
        path5.lineTo(215, 350);
        path5.lineTo(185, 350);
        path5.close();
        canvas.drawPath(path5, paint);
        /* 寫字 */
        paint.setTextSize(24);
        canvas.drawText("圓形", 240, 50,
                paint);
        canvas.drawText("正方形", 240, 120,
                paint);
        canvas.drawText("長方形", 240, 190,
                paint);
        canvas.drawText("橢圓形", 240, 250,
                paint);
        canvas.drawText("三角形", 240, 320,
                paint);
        canvas.drawText("梯形", 240, 390,
                paint);
    }
    public void show() {
        wm.addView(this, params);
    }
}