ColorProgress

类似百度手机助手的下载进度条。

虽然 gif 有些不平滑，但实际手机上是平滑的。。。

这种简单的自定义 View ，其实就是拼一个 background 。

public class ColorProgress extends TextView {

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

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

    public ColorProgress(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    // 三层 Drawable，重叠的实现
    private Drawable floor0;
    private Drawable floor1;
    private Drawable floor2;

    // 二层 ClipDrawable，进度条的实现
    private ClipDrawable clipDrawable1;
    private ClipDrawable clipDrawable2;

    //

    final int cornerRadius = 100;
    final int strokeWidth = 4;
    // 进度条的内边距
    final int inset1 = 12;
    final int inset2 = 4;

    int progressColor;

    private void initProgressColor() {
        progressColor = getResources().getColor(android.R.color.holo_blue_light);
    }

    //

    private void initFloor0() {
        GradientDrawable gradientDrawable = new GradientDrawable();
        gradientDrawable.setCornerRadius(cornerRadius);
        gradientDrawable.setStroke(strokeWidth, progressColor);
        floor0 = gradientDrawable;
    }

    private void initFloor1() {
        GradientDrawable gradientDrawable = new GradientDrawable();
        gradientDrawable.setCornerRadius(cornerRadius);
        gradientDrawable.setColor(progressColor);
        clipDrawable1 = new ClipDrawable(gradientDrawable, Gravity.START, ClipDrawable.HORIZONTAL);
        floor1 = new InsetDrawable(clipDrawable1, inset1);
    }

    private void initFloor2() {
        GradientDrawable gradientDrawable = new GradientDrawable();
        gradientDrawable.setCornerRadius(cornerRadius);
        gradientDrawable.setColor(progressColor);
        // second 进度条设置透明度
        gradientDrawable.setAlpha(100);
        clipDrawable2 = new ClipDrawable(gradientDrawable, Gravity.START, ClipDrawable.HORIZONTAL);
        floor2 = new InsetDrawable(clipDrawable2, inset2);
    }

    //

    private void init() {
        initProgressColor();
        initFloor0();
        initFloor1();
        initFloor2();

        Drawable[] d = new Drawable[]{floor0, floor1, floor2};
        LayerDrawable layerDrawable = new LayerDrawable(d);
        setBackground(layerDrawable);

        setTextColor(Color.WHITE);
    }

    //

    public void setProgress(float fraction) {
        clipDrawable1.setLevel((int) (fraction * 10000));
    }

    public void setSecondProgress(float fraction) {
        clipDrawable2.setLevel((int) (fraction * 10000));
    }

    public void clear() {
        clipDrawable1.setLevel(0);
        clipDrawable2.setLevel(0);
    }

}

MainActivity 模拟下载进度

public class MainActivity extends AppCompatActivity {

    ColorProgress progress;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        progress = (ColorProgress) findViewById(R.id.progress);
        progress.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startAnim();
            }
        });
    }

    private void startAnim() {
        progress.clear();
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(0);
        valueAnimator.setDuration(5000);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float f = animation.getAnimatedFraction();
                progress.setSecondProgress(f);
                if (f > 0.2) {
                    progress.setProgress(f - 0.2f);
                }
                progress.setText((int) (f * 100) + " %");
                if (f == 1) {
                    startAnim2();
                }
            }
        });
        valueAnimator.start();
    }

    private void startAnim2() {
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(0);
        valueAnimator.setDuration(1000);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float f = animation.getAnimatedFraction();
                progress.setProgress(0.8f + f * 0.2f);
                if (f == 1) {
                    progress.setText("安装");
                }
            }
        });
        valueAnimator.start();
    }

用了这么多 Drawable 会不会很消耗性能之类的问题？

我也不清楚。。。

InsetDrawable 和 ClipRrawable 都属于 DrawableWrapper ，并不参与绘制。

InsetDrawable 会压缩实际绘制 Drawable 的 bounds ， ClipRrawable 则是只绘制 Drawable 的一部分。

实质是 ，根据 level 不断调整 clipRect(r) 中 r 的大小，然后重绘。