来源: 互联网  发布时间: 2014-02-18

困扰很久的问题 挺纠结的 help啊。
我自定义了一个Scroller继承了ViewGroup 这个控件实现的功能就像android桌面那种滚动效果，然后我在activity给我自定义的Scroller添加了元素，分成了几页，我想在我添加的某个元素上显示当前的页码，我不知道代码到底在哪里写，该怎么写？

//这是自定义的控件

package org.bluemedia.constom;

import org.bluemedia.R;
import org.bluemedia.activities.Brand_search;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class ScrollLayout extends ViewGroup {

    private static final String TAG = "ScrollLayout";

    private Scroller mScroller;

    private VelocityTracker mVelocityTracker;

    private int mCurScreen;

    private int mDefaultScreen = 0;

    private static final int TOUCH_STATE_REST = 0;

    private static final int TOUCH_STATE_SCROLLING = 1;

    private static final int SNAP_VELOCITY = 600;

    private int mTouchState = TOUCH_STATE_REST;

    private int mTouchSlop;

    private float mLastMotionX;
    private float mLastMotionY;

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

    public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScroller = new Scroller(context);
        mCurScreen = mDefaultScreen;
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        if (changed) {
            int childLeft = 0;
            final int childCount = getChildCount();

            for (int i = 0; i < childCount; i++) {
                View childView = getChildAt(i);
                if (childView.getVisibility() != View.GONE) {
                    final int childWidth = childView.getMeasuredWidth();
                    childView.layout(childLeft, 0, childLeft + childWidth,
                            childView.getMeasuredHeight());
                    childLeft += childWidth;
                } else {
                    removeView(childView);
                }
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        Log.e(TAG, "onMeasure");
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);

        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException(
                    "ScrollLayout only canmCurScreen run at EXACTLY mode!");
        }

        // final int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        // if (heightMode != MeasureSpec.EXACTLY) {
        // throw new IllegalStateException(
        // "ScrollLayout only can run at EXACTLY mode!");
        // }

        // The children are given the same width and height as the scrollLayout
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }

        // Log.e(TAG, "moving to screen "+mCurScreen);
        scrollTo(mCurScreen * width, 0);
    }

    /**
     * 
     * According to the position of current layout
     * 
     * scroll to the destination page.
     */
    public void snapToDestination() {
        final int screenWidth = getWidth();
        final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
        snapToScreen(destScreen);
    }

    public void snapToScreen(int whichScreen) {
        // get the valid layout page
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));

        if (getScrollX() != (whichScreen * getWidth())) {
            final int delta = whichScreen * getWidth() - getScrollX();
            mScroller.startScroll(getScrollX(), 0, delta, 0,
                    Math.abs(delta) * 2);
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout
        }
    }

    public void setToScreen(int whichScreen) {
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        mCurScreen = whichScreen;
        scrollTo(whichScreen * getWidth(), 0);
    }

    public int getCurScreen() {
        return mCurScreen;
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(event);

        final int action = event.getAction();
        final float x = event.getX();
        final float y = event.getY();

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            Log.e(TAG, "event down!");
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }
            mLastMotionX = x;
            break;
        case MotionEvent.ACTION_MOVE:
            int deltaX = (int) (mLastMotionX - x);
            mLastMotionX = x;
            scrollBy(deltaX, 0);
            break;
        case MotionEvent.ACTION_UP:
            Log.e(TAG, "event : up");
            final VelocityTracker velocityTracker = mVelocityTracker;
            velocityTracker.computeCurrentVelocity(1000);
            int velocityX = (int) velocityTracker.getXVelocity();
            Log.e(TAG, "velocityX:" + velocityX);

            if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
                Log.e(TAG, "snap left");
                snapToScreen(mCurScreen - 1);
                System.err.println("11");
            } else if (velocityX < -SNAP_VELOCITY
                    && mCurScreen < getChildCount() - 1) {
                Log.e(TAG, "snap right");
                snapToScreen(mCurScreen + 1);
                System.err.println("2");
            } else {
                snapToDestination();
            }
            mTouchState = TOUCH_STATE_REST;
            break;
        case MotionEvent.ACTION_CANCEL:
            mTouchState = TOUCH_STATE_REST;
            break;
        }
        return true;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop + "; action = "
                + ev.getAction());
        final int action = ev.getAction();

        if ((action == MotionEvent.ACTION_MOVE)
                && (mTouchState != TOUCH_STATE_REST)) {
            Log.e(TAG, "onInterceptTouchEvent-action:" + action);
            return true;
        }

        final float x = ev.getX();
        final float y = ev.getY();

        switch (action) {
        case MotionEvent.ACTION_MOVE:
            final int xDiff = (int) Math.abs(mLastMotionX - x);
            Log.e(TAG, "onInterceptTouchEvent-move: xDiff = " + xDiff
                    + "; mLastMotionX = " + mLastMotionX);
            if (xDiff > mTouchSlop) {
                mTouchState = TOUCH_STATE_SCROLLING;
            }
            break;
        case MotionEvent.ACTION_DOWN:
            mLastMotionX = x;
            mLastMotionY = y;
            Log.e(TAG, "onInterceptTouchEvent-down: x = " + x + "; y = " + y);
            mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
                    : TOUCH_STATE_SCROLLING;
            break;
        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            Log.e(TAG, "onInterceptTouchEvent-up: mLastMotionX = "
                    + mLastMotionX);
            mTouchState = TOUCH_STATE_REST;
            break;
        }
        return mTouchState != TOUCH_STATE_REST;
    }

}

//这是我的activity
scrollLayout = (ScrollLayout)findViewById(R.id.ScrollLayoutTest);
        ImageView img1=(ImageView)findViewById(R.id.img1);
        ImageView img2=(ImageView)findViewById(R.id.img2);
        ImageView img3=(ImageView)findViewById(R.id.img3);
        img4=(Button)findViewById(R.id.img4);
        ImageView img5=(ImageView)findViewById(R.id.img5);
        ImageView img6=(ImageView)findViewById(R.id.img6);
        ImageView img7=(ImageView)findViewById(R.id.img7);
        DisplayMetrics dm = new DisplayMetrics();
        // 取得窗口属性
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        // 窗口的宽度
        screenWidth = dm.widthPixels;
        // 图片宽度
        imgWidth = BitmapFactory.decodeResource(getResources(),
                R.drawable.bg_pinpai_fenlei).getWidth();
        // 获取中间的空隙
        paddingWidth = (screenWidth/4-imgWidth)/2;
        
        //得到总页数
        if(count%pageSize!=0){
            page=count/pageSize+1;
        }else{
            page=count/pageSize;
        }
        switch (page) {
        case 2:
            img3.setVisibility(1);
            break;
        case 3:
            img2.setVisibility(1);
            img3.setVisibility(1);
            break;
        case 4:
            img5.setVisibility(0);
            img2.setVisibility(1);
            img3.setVisibility(1);
            break;
        case 5:
            img6.setVisibility(1);
            img5.setVisibility(1);
            img2.setVisibility(1);
            img3.setVisibility(1);
            break;
        case 6:
            img7.setVisibility(1);
            img6.setVisibility(1);
            img5.setVisibility(1);
            img2.setVisibility(1);
            img3.setVisibility(1);
            break;
        case 1:
            img4.setText("1");
            break;
        default:
            img1.setVisibility(1);
            img7.setVisibility(1);
            img6.setVisibility(1);
            img5.setVisibility(1);
            img2.setVisibility(1);
            img3.setVisibility(1);
            break;
        }
        img4.setText("1");
        int a=0;  
        //循环给控件添加元素
        breakFor:for(int i=0;i<page;i++){
            TableLayout table =new TableLayout(this);
            for(int j=0;j<4;j++){//显示4行4列
                TableRow row=new TableRow(this);
                 for(int k=0;k<4;k++){
                    a++;
                    ImageView img=new ImageView(this);
                    img.setPadding(paddingWidth, 20, paddingWidth, 20);
                    img.setImageResource(R.drawable.bg_pinpai_fenlei);
                    row.addView(img);
                    if(count==a){
                        table.addView(row);
                        scrollLayout.addView(table);
                        break breakFor;//跳到最外层
                    }
                } 

                table.addView(row);
            }
            scrollLayout.addView(table);
        }

    

    来源: 互联网  发布时间: 2014-02-18

RatingBar显示不全的问题

在一个项目中，用到了RatingBar控件，布局用的是RelativeLayout，运行起来，发现星星总是显示不全，要么少一个星，要么高度被遮。原来是自己不小心引起的，布局文件RatingBar的控件用了android:padding="10dp"这个属性，把它去掉就可以了。

小结一下，不知你是否也因为自己的不小心遇上类似的问题呢？细心检查下布局文件看看，希望能帮到你！

    

    来源: 互联网  发布时间: 2014-02-18

java软引用(softReference)类型在listview中的一个应用

由于java的回收机制，使得程序员对内存的引用的回收是不可预测的。而这里就可以做做文章了，讲解SoftReference在一方面的应用（对于有些技术，我感觉只学有用的，不学用不到的。这有别于学os原理，比如os原理你最好精通，这样你的编程内功就会很强，具体的招式则到用到时再学习，或者用不到的就没必要去学）。在android编程中，特别是在listview用来显示来自网络的图片等需要异步加载的资源时，往往需要一个优化的机制。第一是异步加载，这个看我的一篇收藏的博客”Android实现ListView异步加载图片”。第二则是既要考虑到手机的内存问题，又要考虑到网络下载的问题，就是当你下载了一张图片，然后显示在listview的一个view上，然后执行往下拉又往回拉这个动作时，那么我们是否重新去下载该图片呢？好处是节省内存，你每次就存着显示在界面上的那几幅图，但是坏处是每次更新都要重新下载图片。所以我们需要一个缓存的机制，当只有图片的url（即图片的引用）不存在缓存中时才去下载。当然，当内存告急时，需要释放一些没引用的图片，这样，SoftReference就可以很大的用武之地了。即将下载下来的图片放在SoftReference中，然后用map，用Key=img_url来存储该软连接。