android實現文字漸變效果和歌詞進度的效果

要用TextView使用漸變色，那我們就必須要了解LinearGradient（線性漸變）的用法。

LinearGradient的參數解釋

LinearGradient也稱作線性渲染，LinearGradient的作用是實現某一區域內顏色的線性漸變效果，看源碼你就知道他是shader的子類。

它有兩個構造函數

public LinearGradient(float x0, float y0, float x1, float y1, int color0, int color1, Shader.TileMode tile)


public LinearGradient (float x0, float y0, float x1, float y1, int[] colors, float[] positions, Shader.TileMode tile);

其中，參數x0表示漸變的起始點x坐標；參數y0表示漸變的起始點y坐標；參數x1表示漸變的終點x坐標；參數y1表示漸變的終點y坐標　；color0表示漸變開始顏色；color1表示漸變結束顏色；參數tile表示平鋪方式。

Shader.TileMode有3種參數可供選擇，分別為CLAMP、REPEAT和MIRROR：

CLAMP的作用是如果渲染器超出原始邊界范圍，則會復制邊緣顏色對超出范圍的區域進行著色

REPEAT的作用是在橫向和縱向上以平鋪的形式重復渲染位圖

MIRROR的作用是在橫向和縱向上以鏡像的方式重復渲染位圖

LinearGradient的簡單使用

先實現文字效果的水平漸變：

Shader shader_horizontal= new LinearGradient(btWidth/4, 0, btWidth, 0, Color.RED, Color.GREEN, Shader.TileMode.CLAMP);
                tv_text_horizontal.getPaint().setShader(shader_horizontal);

再實現文字的垂直漸變效果：

Shader shader_vertical=new LinearGradient(0, btHeight/4, 0, btHeight, Color.RED, Color.GREEN, Shader.TileMode.CLAMP);
                tv_text_vertical.getPaint().setShader(shader_vertical);

接下來來實現文字的顏色動態漸變效果：<喎?/kf/ware/vc/" target="_blank" class="keylink">vcD4NCjxwcmUgY2xhc3M9"brush:java;"> import android.content.Context; import android.graphics.Canvas; import android.graphics.LinearGradient; import android.graphics.Matrix; import android.graphics.Paint; import android.graphics.Shader; import android.util.AttributeSet; import android.widget.TextView; /** * Created on 2016/3/13. */ public class GradientHorizontalTextView extends TextView { private LinearGradient mLinearGradient; private Matrix mGradientMatrix;//漸變矩陣 private Paint mPaint;//畫筆 private int mViewWidth = 0;//textView的寬 private int mTranslate = 0;//平移量 private boolean mAnimating = true;//是否動畫 private int delta = 15;//移動增量 public GradientHorizontalTextView(Context ctx) { this(ctx,null); } public GradientHorizontalTextView(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); if (mViewWidth == 0) { mViewWidth = getMeasuredWidth(); if (mViewWidth > 0) { mPaint = getPaint(); String text = getText().toString(); int size; if(text.length()>0) { size = mViewWidth*2/text.length(); }else{ size = mViewWidth; } mLinearGradient = new LinearGradient(-size, 0, 0, 0, new int[] { 0x33ffffff, 0xffffffff, 0x33ffffff }, new float[] { 0, 0.5f, 1 }, Shader.TileMode.CLAMP); //邊緣融合 mPaint.setShader(mLinearGradient);//設置漸變 mGradientMatrix = new Matrix(); } } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); if (mAnimating && mGradientMatrix != null) { float mTextWidth = getPaint().measureText(getText().toString());//獲得文字寬 mTranslate += delta;//默認向右移動 if (mTranslate > mTextWidth+1 || mTranslate<1) { delta = -delta;//向左移動 } mGradientMatrix.setTranslate(mTranslate, 0); mLinearGradient.setLocalMatrix(mGradientMatrix); postInvalidateDelayed(30);//刷新 } } }

實現歌詞進度效果

Canvas 作為繪制文本時，使用FontMetrics對象，計算位置的坐標。它的思路和java.awt.FontMetrics的基本相同。
FontMetrics對象它以四個基本坐標為基准，分別為：

FontMetrics.top
FontMetrics.ascent
FontMetrics.descent
FontMetrics.bottom

// FontMetrics對象
  FontMetrics fontMetrics = textPaint.getFontMetrics();  
  String text = "abcdefghijklmnopqrstu";  
  // 計算每一個坐標
  float baseX = 0;  
  float baseY = 100;  
  float topY = baseY + fontMetrics.top;  
  float ascentY = baseY + fontMetrics.ascent;  
  float descentY = baseY + fontMetrics.descent;  
  float bottomY = baseY + fontMetrics.bottom;  

下面是具體實現代碼：

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created  on 2016/3/13.
 */
public class SongTextView extends View {
    private int postIndex;
    private Paint mPaint;
    private int delta = 15;
    private float mTextHeight;
    private float mTextWidth;
    private String mText="夢 裡 面 看 我 七 十 二 變";
    private PorterDuffXfermode xformode;
    public SongTextView(Context ctx)
    {
        this(ctx,null);
    }
    public SongTextView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public SongTextView(Context context,  AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
    public void init()
    {
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        xformode = new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);
        mPaint.setColor(Color.CYAN);
        mPaint.setTextSize(60.0f);
        mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
        mPaint.setXfermode(null);
        mPaint.setTextAlign(Paint.Align.LEFT);
        //文字精確高度
        Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
        mTextHeight = fontMetrics.bottom-fontMetrics.descent-fontMetrics.ascent;
        mTextWidth  = mPaint.measureText(mText);
    }
    /**
      *計算 控件的寬高
      */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
      final  int mWidth;
      final  int mHeight;
        /**
         * 設置寬度
         */
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        if (widthMode == MeasureSpec.EXACTLY)// match_parent , accurate
            mWidth = widthSize;
        else
        {
            // 由圖片決定的寬
            int desireByImg = getPaddingLeft() + getPaddingRight()
                    + getMeasuredWidth();
            if (widthMode == MeasureSpec.AT_MOST)// wrap_content
                mWidth = Math.min(desireByImg, widthSize);
             else
                mWidth = desireByImg;
        }
        /***
         * 設置高度
         */
        int   heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int   heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if (heightMode == MeasureSpec.EXACTLY)// match_parent , accurate
            mHeight = heightSize;
         else
        {
            int desire = getPaddingTop() + getPaddingBottom()
                    + getMeasuredHeight();
            if (heightMode == MeasureSpec.AT_MOST)// wrap_content
                mHeight = Math.min(desire, heightSize);
             else
                mHeight = desire;
        }
        setMeasuredDimension( mWidth,  mHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Bitmap srcBitmap = Bitmap.createBitmap(getMeasuredWidth(),getMeasuredHeight(), Bitmap.Config.ARGB_8888);
        Canvas srcCanvas = new Canvas(srcBitmap);
        srcCanvas.drawText(mText, 0, mTextHeight, mPaint);
        mPaint.setXfermode(xformode);
        mPaint.setColor(Color.RED);
        RectF rectF = new RectF(0,0,postIndex,getMeasuredHeight());
        srcCanvas.drawRect(rectF, mPaint);
        canvas.drawBitmap(srcBitmap, 0, 0, null);
        init();
        if(postIndex

ProgressBar實現歌詞播放效果

然後接下來的這種歌詞播放進度效果是2張圖片實現的，忘記是哪個那裡看來的，壓根以前也沒有想過還可以這麼樣的實現。
只需要准備2張圖即可：



看見沒就是2張圖片，一張作為背景圖一張作為進度圖，是不是感覺很神奇，然後放入ProgressBar

再加上代碼動態改變progress就能實現進度的變化了：

 ProgressBar pb1= (ProgressBar) findViewById(R.id.pb1);
          //設置滾動條可見
        setProgressBarIndeterminateVisibility(true);
        progress=pb1.getProgress();//獲取初始進度
        timer=new Timer();
        task=new TimerTask() {
            @Override
            public void run() {
                progress+=10;
                if(progress>100){
                    progress=0;
                }
                handler.sendEmptyMessage(0);
            }
        };
        timer.schedule(task,1000,300);

實現及進度的改變：

Handler handler=new Handler(){
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        pb1.setProgress(progress);
    }
};

    @Override
    protected void onDestroy() {
        super.onDestroy();
        timer=null;
        task=null;
        handler.removeCallbacksAndMessages(null);
    }

效果也是不錯的：


能力有限，感覺寫一篇博客要弄好久，網速卡的一筆，就寫到這了，其實項目裡面也沒有用到，休息2天了也寫點東西，就覺得還是要學一點東西作為備用知識。