android GridView 在TV上，上下翻页的时候平滑滑动的实现

ゞ浴缸里的玫瑰 2022-06-12 00:56 251阅读 0赞

应该做过android tv开发的同学都知道，在TV上使用GridView的时候，如果焦点上下移动的时候，如果移动到在屏幕上可见的第一行或者最后一行的时候，如果再继续上下移动，

的话，是比较生硬呆滞的的上下滚动页面，焦点移动到下一个item上，这是非常不太好的体验效果，我们要的是比较平滑的滚动效果。

首先我们要来了解一下GridView的如下这个方法:

smoothScrollToPositionFromTop(int position,int offset,int duration);

滚动到position项目的位置，并且position项目距离GirdView上边的距离为offset个像素，duration指定滚动需要的时间（毫秒）。

这个方法是今天的主角，虽然是主角，但不是说只有使用这个方法就可以了？当然不是，当然也需要一定的逻辑算法配合。

今天就说说我是如何实现的。

先说说我的思路：

首先你要知道当前item所在的行，才知道按上下按键的时候，要滚动到哪一个postion。

public class AppsGridViewAdapter extends BaseAdapter {
    	private int mCurrentSelectedPosition = 0;
    	private int mLastSelectedPosition = 0;
    	private static final int ITEM_BG_COLORS[] = new int[]{
    		Color.parseColor("#e0c101"),
    		Color.parseColor("#fbaf54"),
    		Color.parseColor("#684cb5"),
    		Color.parseColor("#23a5ba"),
    		Color.parseColor("#03ba9f"),
    		Color.parseColor("#88c04c"),
    		Color.parseColor("#684cb5"),
    		Color.parseColor("#23a5ba"),
    		Color.parseColor("#03ba9f"),
    		Color.parseColor("#88c04c"),
    		Color.parseColor("#e0c101"),
    		Color.parseColor("#fbaf54"),
    	};
    	private int mColorIndex = 0;
    	private List<AppInfo> mApps = new ArrayList<AppInfo>();
    	private Context mContext;
    	private int mGridViewRows = 0;
    	public AppsGridViewAdapter(Context context, List<AppInfo> apps) {
    		this.mContext = context;
    		if(apps!=null)
    			this.mApps = apps;
    		setRows();
    		mColorIndex = 0;
    	}
    
    
    
    	private void setRows() {
    		int remainder = mApps.size() % 6;
    		mGridViewRows =(remainder == 0)? (this.mApps.size() > 0 ?  this.mApps.size() / 6:0) : (mApps.size() / 6) +1;
    	}
    	
    	
    	
    	public int getNumRows() {
    		return mGridViewRows;
    	}
    
    	public int getNumColumns(){
    		return 6;
    	}
    
    
    	@Override
    	public void notifyDataSetChanged() {
    		mColorIndex = 0;
    		super.notifyDataSetChanged();
    	}
    	
    	public void setApps(List<AppInfo> apps){
    		mApps.clear();
    		if(apps!=null)
    			mApps = apps;
    		setRows();
    	}
    	
    	
    	public void addApp(AppInfo app){
    		if(app!=null && app.isValidate())
    			mApps.add(app);
    		setRows();
    	}
    	
    	public void removeApp(AppInfo app){
    		if(app!=null)
    			mApps.remove(app);
    		setRows();
    	}
    	
    	
    	
    	public int getCurrentSelectedPosition() {
    		return mCurrentSelectedPosition;
    	}
    
    
    
    
    	public int getLastSelectedPosition() {
    		return mLastSelectedPosition;
    	}
    
    
    
    
    	@Override
    	public int getCount() {
    		return mApps.size();
    	}
    
    	@Override
    	public Object getItem(int position) {
    		return mApps.get(position);
    	}
    
    	@Override
    	public long getItemId(int position) {
    		return position;
    	}
    
    	@Override
    	public View getView(int position, View convertView, ViewGroup parent) {
    		ViewHolder holder = null;
    		if(convertView == null){
    			 convertView = View.inflate(mContext, R.layout.apps_page_gridview_item_layout, null);
    			 holder = new ViewHolder();
    			 holder.mAppIcon = (ImageView) convertView.findViewById(R.id.app_icon);
    			 holder.mAppName = (TextView) convertView.findViewById(R.id.app_name);
    			 holder.mAppIconColorBg = (RelativeLayout) convertView.findViewById(R.id.app_icon_color_bg);
    			 convertView.setTag(holder);
    		}
    		holder = (ViewHolder) convertView.getTag();
    		holder.mAppName.setText(mApps.get(position).getName());
    		holder.mAppIcon.setBackgroundDrawable(mApps.get(position).getIcon());
    		holder.mAppIconColorBg.setBackgroundColor(ITEM_BG_COLORS[mColorIndex]);
    		++mColorIndex;
    		mColorIndex =( (mColorIndex / 6) != 0 && (mColorIndex / 6) % 2 == 0 ) ? 0 :mColorIndex;
    		return convertView;
    	}
    	
    	private static final class ViewHolder{
    		private ImageView mAppIcon;
    		private TextView mAppName;
    		private RelativeLayout mAppIconColorBg;
    	}
    
    
    }

我们看到，Adapter中定一个了两个方法，可以用来获取多少行，和多少列(列一般是已知的)。

setRows() ;是每次设置给adapter数据的时候，都重新弄设置一下总行数。

getNumRows，返回获取当前所有的行数，getNumColumns返回所有的列数。

OK，接下来，我们就可以通过postion来算出当前选中的postion在哪一行了。

package net.sunniwell.projector.luncher.page;
    
    import java.util.List;
    
    import net.sunniwell.projector.luncher.CategoryPageActivity;
    import net.sunniwell.projector.luncher.R;
    import net.sunniwell.projector.luncher.adapter.AppsGridViewAdapter;
    import net.sunniwell.projector.luncher.bean.AppInfo;
    import net.sunniwell.projector.luncher.engine.PackageAsyncTask;
    import net.sunniwell.projector.luncher.engine.PackageAsyncTask.OnQueryPackageStateListener;
    import net.sunniwell.projector.luncher.engine.PackageEngine;
    import net.sunniwell.projector.luncher.engine.PackageEngine.OnPackageStateChangeListener;
    import net.sunniwell.projector.luncher.views.CommonGridView;
    import android.content.Intent;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AdapterView;
    import android.widget.AdapterView.OnItemClickListener;
    import android.widget.AdapterView.OnItemSelectedListener;
    import android.widget.TextView;
    /**
     * 
     * @author zhanghuagang 2017.7.6
     *
     */
    public class AppsPage extends BasePage implements OnPackageStateChangeListener, OnItemSelectedListener,OnQueryPackageStateListener ,OnItemClickListener{
    	static{
    		sCategory = 3;
    	}
    	private int mCurrentRow = 0;
    	private TextView mIndexTextView;
    	private CommonGridView mGridView;
    	private AppsGridViewAdapter mAppsAdapter;
    	private PackageAsyncTask mAsyncTask;
    	private PackageEngine mPackageEngine;
    	public AppsPage(CategoryPageActivity activity, ViewGroup contentView,int category) {
    		super(activity, contentView, category);
    		this.mPackageEngine = PackageEngine.getDefault(activity);
    		this.mPackageEngine.setOnPackageStateChangeListener(this);
    	}
    	
    	@Override
    	public void initView() {
    		mIndexTextView = (TextView) mContentView.findViewById(R.id.index_textview);
    		mGridView = (CommonGridView) mContentView.findViewById(R.id.apps_gridview);
    		mGridView.setOnItemSelectedListener(this);
    		mGridView.setOnItemClickListener(this);
    		mAppsAdapter = new AppsGridViewAdapter(mActivity,null);
    		mGridView.setAdapter(mAppsAdapter);
    		mAppsAdapter.notifyDataSetChanged();
    	}
    
    	@Override
    	public void onResume() {
    		mPackageEngine.register();
    		queryApps();
    	}
    
    	private void queryApps() {
    		if(mAsyncTask!=null)
    			mAsyncTask.stop();
    		mAsyncTask = new PackageAsyncTask(mActivity, this);
    		mAsyncTask.start();
    	}
    
    	@Override
    	public void onStop() {
    		
    	}
    
    	@Override
    	public void onPause() {
    		mPackageEngine.unregister();
    	}
    
    	@Override
    	public void onDestroy() {
    	}
    	
    	private int getItemIndex(int position){
    				int r = position % mAppsAdapter.getNumColumns() ;
    				if(r  == 0){
    					 if(position > 0 ){
    						  return (position/mAppsAdapter.getNumColumns())+1;
    					 }else{
    						 return 1;
    					 }
    				}else{
    				    return (position/mAppsAdapter.getNumColumns())+1;
    				}
    	}
    
    	@Override
    	public void onItemSelected(AdapterView<?> parent, View view, int position,
    			long id) {
    		if(getItemIndex(position) > mCurrentRow){
    			mGridView.smoothScrollToPositionFromTop(position, 0,500);
    		}else if(getItemIndex(position) < mCurrentRow){
    			mGridView.smoothScrollToPositionFromTop(position-2, 0,500);
    		}
    		mGridView.onItemSelected(parent, view, position, id);
    		mIndexTextView.setText(getItemIndex(position)+"  |  "+mAppsAdapter.getNumRows());
    		mCurrentRow =getItemIndex(position); 
    	}
    
    	@Override
    	public void onNothingSelected(AdapterView<?> parent) {
    		
    	}
    
    	@Override
    	public void onFinish(List<AppInfo> apps) {
    			mAppsAdapter.setApps(apps);
    			mAppsAdapter.notifyDataSetChanged();
    	}
    
    	@Override
    	public void onItemClick(AdapterView<?> parent, View view, int position,long id) {
    		AppInfo app = (AppInfo) mAppsAdapter.getItem(position);
    		if(app!=null){
    			final Intent intent = new Intent();
    			intent.setClassName(app.packageName, app.className);
    			intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    			mActivity.startActivity(intent);
    		}
    	}
    
    	@Override
    	public void onPackageAdded(AppInfo app) {
    		mAppsAdapter.addApp(app);
    		mAppsAdapter.notifyDataSetChanged();
    	}
    
    	@Override
    	public void onPackageDeleted(AppInfo app) {
    		mAppsAdapter.removeApp(app);
    		mAppsAdapter.notifyDataSetChanged();
    	}
    }

我的getItemIndex(int postion)就是根据position获取当前所在行的。

然后我们在onItemSelected对平滑滑动做处理。

如果下一个获取焦点的item所在行小于当前行，说明是向上按的，如果是大于当前行，说明是向下按住的。

这里我们特殊的处理的向下按的，position-2，这个意思就是当我向下按的时候，每次移动两个postion的距离，并且postion和边缘距离为0