Android 滑动改变top颜色

来源：互联网发布：中小型企业网络建设编辑：程序博客网时间：2024/06/14 01:50

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/**
* 带滚动监听的scrollview
*
*/
public class ObservableScrollView extends ScrollView {

public interface ScrollViewListener {    void onScrollChanged(ObservableScrollView scrollView, int x, int y,            int oldx, int oldy);}private ScrollViewListener scrollViewListener = null;public ObservableScrollView(Context context) {    super(context);}public ObservableScrollView(Context context, AttributeSet attrs,        int defStyle) {    super(context, attrs, defStyle);}public ObservableScrollView(Context context, AttributeSet attrs) {    super(context, attrs);}public void setScrollViewListener(ScrollViewListener scrollViewListener) {    this.scrollViewListener = scrollViewListener;}@Overrideprotected void onScrollChanged(int x, int y, int oldx, int oldy) {    super.onScrollChanged(x, y, oldx, oldy);    if (scrollViewListener != null) {        scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);    }}

public class MainActivity extends Activity implements ScrollViewListener{

private ObservableScrollView scrollView;private ListView listView;private ImageView imageView;private TextView textView;private int imageHeight;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    scrollView = (ObservableScrollView) findViewById(R.id.scrollview);    listView = (ListView) findViewById(R.id.listview);    imageView = (ImageView) findViewById(R.id.imageview);    textView = (TextView) findViewById(R.id.textview);    initListeners();    initData();}private void initListeners() {    // 获取顶部图片高度后，设置滚动监听    ViewTreeObserver vto = imageView.getViewTreeObserver();    vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {        @Override        public void onGlobalLayout() {            imageView.getViewTreeObserver().removeGlobalOnLayoutListener(                    this);            imageHeight = imageView.getHeight();            scrollView.setScrollViewListener(MainActivity.this);        }    });}private void initData() {    ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.data));    listView.setAdapter(adapter);}@Overridepublic void onScrollChanged(ObservableScrollView scrollView, int x, int y,        int oldx, int oldy) {    // TODO Auto-generated method stub    // Log.i("TAG", "y--->" + y + "    height-->" + height);    if (y <= 0) {        textView.setBackgroundColor(Color.argb((int) 0, 227, 29, 26));//AGB由相关工具获得，或者美工提供    } else if (y > 0 && y <= imageHeight) {        float scale = (float) y / imageHeight;        float alpha = (255 * scale);        // 只是layout背景透明(仿知乎滑动效果)        textView.setBackgroundColor(Color.argb((int) alpha, 227, 29, 26));    } else {        textView.setBackgroundColor(Color.argb((int) 255, 227, 29, 26));    }}

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