android 自定义gridview（导航）

最近又重新做回安卓，做了个小项目。下绝心使用android studio，通过这一回实战，终于用上了。综合了前人的经验，搞了个自己满意的导航界面，用的是gridview。

代码：

package com.cquni.control;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.widget.AbsListView;
import android.widget.GridView;

import com.cquni.smartwcs.R;

/*
用来做导航的自定义GridView
 */
public class NavigateGridView extends GridView {
    private Bitmap background;
    private int img_Id = R.drawable.gridbg;
    public NavigateGridView(Context context) {
        super(context);
        background = BitmapFactory.decodeResource(getResources(), img_Id);
    }

    public NavigateGridView(Context context, AttributeSet attrs) {
        super(context, attrs);
        background = BitmapFactory.decodeResource(getResources(), img_Id);
    }

    public NavigateGridView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        background = BitmapFactory.decodeResource(getResources(), img_Id);
    }

    /*
    高度实现自适应
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int heightSpec;
        if (getLayoutParams().height == AbsListView.LayoutParams.WRAP_CONTENT) {
            heightSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
        } else {
            heightSpec = heightMeasureSpec;
        }
        super.onMeasure(widthMeasureSpec, heightSpec);
    }

    /*
    拉伸背景图
     */
    @Override
    protected void dispatchDraw(Canvas canvas) {
        int count = getChildCount();
        int top = count > 0 ? getChildAt(0).getTop() : 0;
        int backgroundWidth = background.getWidth();
        int backgroundHeight = background.getHeight();
        int width = getWidth();
        int height = getHeight();
        final Rect src = new Rect();
        src.left = 0;
        src.top = 0;
        src.right = backgroundWidth;
        src.bottom = backgroundHeight;
        for (int y = top; y < height; y += backgroundHeight) {
            RectF dst = new RectF();
            dst.left = 0;
            dst.top = y;
            dst.right = width;
            dst.bottom = (y + backgroundHeight) / 2;
            canvas.drawBitmap(background, src, dst, null);
        }
        super.dispatchDraw(canvas);
    }
}

gridview改进：

gv.setSelector(new ColorDrawable(Color.TRANSPARENT));

选中item时的动画

ImageView itemImg = arg1.findViewById(R.id.ItemImageView);
Animation animation = AnimationUtils.loadAnimation(MainActivity.this, R.anim.item_img);
itemImg.startAnimation(animation);

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <alpha
        android:fromAlpha="0.5"
        android:toAlpha="1.0"
        android:duration="50"/>
</set>