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在开发过程中，咱们可能会常常遇到这样的需要款式：
这张图是截取京东音讯告诉的弹出框，咱们能够看到右上方有个三角形的气泡成果，这只是其中一种，三角形的方向还能够是上、下、左、右。
通过截图能够发现，气泡由正三角形和圆角长方形组成，于是能够通过组合来造成三角形气泡的成果，上面咱们通过三种形式进行实现。
实现形式：
1、通过.9 图进行实现；2、通过 shape 形式实现；3、通过自定义 view 的形式实现；实现逻辑：
1、通过.9 图进行实现
这种形式就不用说了吧，找你们 UI 小姐姐切一个.9 图，应用即可，不过这种形式的图片须要占肯定体积哦。
2、通过 shape 形式实现
- 正三角形
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<rotate
android:fromDegrees="45"
android:pivotX="-40%"
android:pivotY="80%">
<shape android:shape="rectangle">
<size
android:width="15dp"
android:height="15dp" />
<solid android:color="#ffffff" />
</shape>
</rotate>
</item>
</layer-list>- 倒三角形
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<rotate
android:fromDegrees="45"
android:pivotX="135%"
android:pivotY="15%">
<shape android:shape="rectangle">
<size
android:width="15dp"
android:height="15dp" />
<solid android:color="#ffffff" />
</shape>
</rotate>
</item>
</layer-list>- 左三角形
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<rotate
android:fromDegrees="-45"
android:pivotX="85%"
android:pivotY="-35%">>
<shape android:shape="rectangle">
<size
android:width="15dp"
android:height="15dp" />
<solid android:color="#ffffff" />
</shape>
</rotate>
</item>
</layer-list>- 右三角形
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<rotate
android:fromDegrees="-45"
android:pivotX="15%"
android:pivotY="135%">>
<shape android:shape="rectangle">
<size
android:width="15dp"
android:height="15dp" />
<solid android:color="#ffffff" />
</shape>
</rotate>
</item>
</layer-list>下面就是通过 shape 形式实现各个方向的代码，这种形式毛病比拟显著，如果要变动不同的角的地位须要再写不同的布局。
3、通过自定义 view 的形式实现
因为是比较简单这里就不解说每个怎么搞了，能够复制过来间接用
- 增加自定义属性
<declare-styleable name="TriangleView">
<attr name="trv_color" format="color" />
<attr name="trv_direction">
<enum name="top" value="0" />
<enum name="bottom" value="1" />
<enum name="right" value="2" />
<enum name="left" value="3" />
</attr>
</declare-styleable>- 自定义代码文件
public class TriangleView extends View {
private static final int TOP = 0;
private static final int BOTTOM = 1;
private static final int RIGHT = 2;
private static final int LEFT = 3;
private static final int DEFUALT_WIDTH = 10;
private static final int DEFUALT_HEIGHT = 6;
private static final int DEFUALT_COLOR = R.color.FFF;
private Paint mPaint;
private int mColor;
private int mWidth;
private int mHeight;
private int mDirection;
private Path mPath;
public TriangleView(final Context context) {this(context, null);
}
public TriangleView(Context context, @Nullable AttributeSet attrs) {this(context, attrs, 0);
}
public TriangleView(final Context context, final AttributeSet attrs, final int defStyleAttr) {super(context, attrs, defStyleAttr);
init();
TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.TriangleView, 0, 0);
mColor = typedArray.getColor(R.styleable.TriangleView_trv_color, ContextCompat.getColor(getContext(), DEFUALT_COLOR));
mDirection = typedArray.getInt(R.styleable.TriangleView_trv_direction, mDirection);
typedArray.recycle();
mPaint.setColor(mColor);
}
private void init() {mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.FILL);
mPath = new Path();
mDirection = TOP;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mWidth = MeasureSpec.getSize(widthMeasureSpec);
mHeight = MeasureSpec.getSize(heightMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (mWidth == 0 || widthMode != MeasureSpec.EXACTLY) {mWidth = (int) PixelUtil.dp2px(DEFUALT_WIDTH);
}
if (mHeight == 0 || heightMode != MeasureSpec.EXACTLY) {mHeight = (int) PixelUtil.dp2px(DEFUALT_HEIGHT);
}
setMeasuredDimension(mWidth, mHeight);
}
@Override
protected void onDraw(Canvas canvas) {super.onDraw(canvas);
switch (mDirection) {
case TOP:
mPath.moveTo(0, mHeight);
mPath.lineTo(mWidth, mHeight);
mPath.lineTo(mWidth / 2, 0);
break;
case BOTTOM:
mPath.moveTo(0, 0);
mPath.lineTo(mWidth / 2, mHeight);
mPath.lineTo(mWidth, 0);
break;
case RIGHT:
mPath.moveTo(0, 0);
mPath.lineTo(0, mHeight);
mPath.lineTo(mWidth, mHeight / 2);
break;
case LEFT:
mPath.moveTo(0, mHeight / 2);
mPath.lineTo(mWidth, mHeight);
mPath.lineTo(mWidth, 0);
break;
default:
break;
}
mPath.close();
canvas.drawPath(mPath, mPaint);
}
}- 布局文件增加
<com.sjl.keeplive.triange.TriangleView
android:layout_width="10dp"
android:layout_height="6dp"
app:trv_color="@color/FFF"
app:trv_direction="top" />通过自定义的形式能够搞定四个方向，而且在代码中也能够应用，动静增加，动静扭转色彩，还是比拟好的形式。
到这里就实现啦.
正文完
