android开发之简单的自定义view

自定义view是安卓开发进阶中的重要阶段。所以想在这方面多花些时间看看,写写。

自定义view的步骤:

1、自定义View的属性
2、在View的构造方法中获得我们自定义的属性
3、重写onMesure
4、重写onDraw
1、自定义View的属性,首先在res/values/ 下建立一个attrs.xml , 在里面定义我们的属性和声明我们的整个样式。


            
            
            
           
               
                      
                    
                
        

定义了字体,字体颜色,字体大小3个属性,format是值该属性的取值类型;

2、创建自定义View继承view ,在构造方法中,获得我们的自定义的样式

/**
 *          自定义View
 * Created by zzj on 2016/11/14.
 */
public class CustomView extends View {
    private static final String TAG = "customview";
    private String mTitleText;
    /**
     * 文本的颜色
     */
    private int mTitleTextColor;
    /**
     * 文本的大小
     */
    private int mTitleTextSize;

    /**
     * 绘制时控制文本绘制的范围
     */
    private Rect mBound;
    private Paint mPaint;

    public CustomView(Context context) {
        this(context,null);
    }

    public CustomView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public CustomView(final Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        /**
         * 获得我们所定义的自定义样式属性
         */
        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomView, defStyleAttr, 0);
        int n = a.getIndexCount();
        for (int i = 0; i < n; i++)
        {
            int attr = a.getIndex(i);
            switch (attr)
            {
                case R.styleable.CustomView_text:
                    mTitleText = a.getString(attr);
                    break;
                case R.styleable.CustomView_textcolor:
                    // 默认颜色设置为黑色
                    mTitleTextColor = a.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.CustomView_textsize:
                    // 默认设置为16sp,TypeValue也可以把sp转化为px
                    mTitleTextSize = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(
                            TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
                    break;

            }

        }
        a.recycle();

        /**
         * 获得绘制文本的宽和高
         */
        mPaint = new Paint();
        mPaint.setTextSize(mTitleTextSize);
        // mPaint.setColor(mTitleTextColor);
        mBound = new Rect();
        mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);

        //添加点击事件
        this.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {

                Toast.makeText(context,TAG,Toast.LENGTH_SHORT).show();

            }
        });
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        Log.d(TAG,"onMeasure----------");
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        Log.d(TAG,"widthMode:"+widthMode+"widthSize:"+widthSize+"heightMode:"+heightMode+"heightSize:"+heightSize);
        int width;
        int height ;
        if (widthMode == MeasureSpec.EXACTLY)
        {
            width = widthSize;
        } else
        {
            mPaint.setTextSize(mTitleTextSize);
            mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
            float textWidth = mBound.width();
            int desired = (int) (getPaddingLeft() + textWidth + getPaddingRight());
            width = desired;
        }

        if (heightMode == MeasureSpec.EXACTLY)
        {
            height = heightSize;
        } else
        {
            mPaint.setTextSize(mTitleTextSize);
            mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
            float textHeight = mBound.height();
            int desired = (int) (getPaddingTop() + textHeight + getPaddingBottom());
            height = desired;
        }



        setMeasuredDimension(width, height);

    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        Log.d(TAG,"onLayout----------");
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Log.d(TAG,"onDraw----------");
        mPaint.setColor(Color.YELLOW);
        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);

        mPaint.setColor(mTitleTextColor);
        canvas.drawText(mTitleText, getWidth() / 2 - mBound.width() / 2, getHeight() / 2 + mBound.height() / 2, mPaint);
    }
}

我们重写了3个构造方法,默认的布局文件调用的是两个参数的构造方法,所以记得让所有的构造调用我们的三个参数的构造,我们在三个参数的构造中获得自定义属性。重写了onMeasure和onDraw方法
onMeasure方法:
系统帮我们测量的高度和宽度都是MATCH_PARNET,当我们设置明确的宽度和高度时,系统帮我们测量的结果就是我们设置的结果,当我们设置为WRAP_CONTENT,或者MATCH_PARENT系统帮我们测量的结果就是MATCH_PARENT的长度。
所以,当设置了WRAP_CONTENT时,我们需要自己进行测量,即重写onMesure方法”;
在onDraw方法中进行绘制;

3.然后在布局中声明我们的自定义View




    
    

运行效果:

android开发之简单的自定义view_第1张图片
IUTH5S(B{OJ8A{)QH4KGQSF.png

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