Question

我在电视上实现了Android应用。在电视上，我们可以通过遥控器上的箭头按钮导航项目。问题是：我有一个ListView，当我浏览列表时，我想在聚焦或选择时使项目更大。这是我的演示代码：

public class MainActivity extends ActionBarActivity implements OnItemSelectedListener {
    private static String TAG = "MainActivity";
    private String[] mMonths = {"January" , "February", "March", "April", "May", "June", "July", 
            "August", "September", "October", "November", "December"};
    private ListView mListView;
    private CustomAdapter mAdapter;
    private View mPre = null;
    private int mHeight;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ArrayList<String> list = new ArrayList<String>(Arrays.asList(mMonths));
        mAdapter = new CustomAdapter(this, list);
        mListView = (ListView) findViewById(R.id.list);
        mListView.setAdapter(mAdapter);
        mListView.setOnItemSelectedListener(this);      
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position,
            long id) {
        // TODO Auto-generated method stub
        Log.e(TAG, "onItemSelected position " + position);
        LayoutParams params = (LayoutParams) view.getLayoutParams();
        float height = getResources().getDisplayMetrics().density * 80;// Bigger height
        params.height = (int) height;
        view.invalidate();
        if(mPre != null){
            height = getResources().getDisplayMetrics().density * 50; //Default height 
            params = (LayoutParams) mPre.getLayoutParams();
            params.height = (int) height;
        }
        mPre = view;
        mPre.invalidate();
        mListView.invalidate();
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub
        Log.e(TAG, "onNothingSelected");
    }

我的CustomAdpater.java

public class CustomAdapter extends BaseAdapter{

    private ArrayList<String> mMonths;
    private Context mContext;
    public CustomAdapter(Context context, ArrayList<String> arrays){
        mContext = context;
        mMonths = arrays;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return mMonths.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return mMonths.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        if(convertView == null)
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);          

        ((TextView) convertView.findViewById(R.id.tv)).setText(mMonths.get(position));
        convertView.setTag(position);
        return convertView;
    }

}

我的item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:background="@drawable/lv_selector"
    android:gravity="center">

    <TextView 
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_margin="5dp"
        android:gravity="center"
        android:textSize="20sp"
        android:background="@color/white"/>

</LinearLayout>

我不知道为什么它不起作用。它不会更改所选项目和上一项目的高度。任何帮助将不胜感激。

Answer 1

我解决了我的问题。不要使用View mPre，从mListView.getChildAt()获取子视图这是我更新的代码，适合任何人需要它。我还制作了平滑的动画。

public class MainActivity extends ActionBarActivity implements OnItemSelectedListener, OnFocusChangeListener {
    private static String TAG = "MainActivity";
    private String[] mMonths = {"January" , "February", "March", "April", "May", "June", "July", 
            "August", "September", "October", "November", "December"};
    private ListView mListView;
    private CustomAdapter mAdapter;
    private int mPrePos = -1;
    private SmoothAnimation mSmoothRunnable;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ArrayList<String> list = new ArrayList<String>(Arrays.asList(mMonths));
        mAdapter = new CustomAdapter(this, list);
        mListView = (ListView) findViewById(R.id.list);
        mListView.setAdapter(mAdapter);
        mListView.setOnItemSelectedListener(this);
        mListView.setOnFocusChangeListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position,
            long id) {
        // TODO Auto-generated method stub
        Log.e(TAG, "onItemSelected position " + position);
        float height;
        LayoutParams params;
        int firstVisiblePos = mListView.getFirstVisiblePosition();
        if(mPrePos != -1 && mListView.getChildAt(mPrePos - firstVisiblePos) != null){
            View child = mListView.getChildAt(mPrePos - firstVisiblePos);           
            height = getResources().getDisplayMetrics().density * 50;
            params = (LayoutParams) child.getLayoutParams();
            params.height = (int) height;
            child.requestLayout();
        }
        mPrePos = position;
        params = (LayoutParams) view.getLayoutParams();
        height = getResources().getDisplayMetrics().density * 100;
//      params.height = (int) height;
        view.post(new SmoothAnimation(view));       
        view.requestLayout();

    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub
        Log.e(TAG, "onNothingSelected");
        int firstVisiblePos = mListView.getFirstVisiblePosition();
        if(mPrePos != -1 && mListView.getChildAt(mPrePos - firstVisiblePos) != null){
            View child = mListView.getChildAt(mPrePos - firstVisiblePos);           
            float height = getResources().getDisplayMetrics().density * 50;
            LayoutParams params = (LayoutParams) child.getLayoutParams();
            params.height = (int) height;
            child.requestLayout();
            mPrePos = -1 ;
        }
    }

    @Override
    public void onFocusChange(View v, boolean hasFocus) {
        // TODO Auto-generated method stub
        int firstVisiblePos = mListView.getFirstVisiblePosition();
        if(v.getId() == R.id.list && hasFocus == false && mPrePos != -1 && mListView.getChildAt(mPrePos - firstVisiblePos) != null){
            View child = mListView.getChildAt(mPrePos - firstVisiblePos);           
            float height = getResources().getDisplayMetrics().density * 50;
            LayoutParams params = (LayoutParams) child.getLayoutParams();
            params.height = (int) height;
            child.requestLayout();
            mPrePos = -1 ;
        }
    }


    private class SmoothAnimation implements Runnable{

        private View mChild;
        private float maxHeight;
        private float minHeight;
        private Interpolator mInterpolator = new LinearInterpolator();
        private final long mDuration = 1000;
        private boolean mContinueRunning = true;
        private long mStartTime = -1;
        private float mCurrentHeight = -1;

        public SmoothAnimation(View child){
            mChild = child;
            maxHeight = mChild.getContext().getResources().getDisplayMetrics().density * 100;
            minHeight = mChild.getContext().getResources().getDisplayMetrics().density * 50;
        }

        @Override
        public void run() {
            // TODO Auto-generated method stub
            if(mStartTime == -1){
                mStartTime = System.currentTimeMillis();
                Log.e(TAG, "current time " + mStartTime);
            }
            else{
                Log.e(TAG, "current time 1 " + System.currentTimeMillis() + " " + mStartTime);
                long nomarlizedTime = 1000 * (System.currentTimeMillis() - mStartTime) / mDuration;
                nomarlizedTime = Math.max(Math.min(nomarlizedTime, 1000), 0);

                float interporlatedHeight = (maxHeight - minHeight) * mInterpolator.getInterpolation(nomarlizedTime / 1000f);
                LayoutParams params = (LayoutParams) mChild.getLayoutParams();
                mCurrentHeight = minHeight + interporlatedHeight;
                Log.e(TAG, "height" + mCurrentHeight);
                params.height = (int) mCurrentHeight;
                mChild.requestLayout();
            }

            if(mContinueRunning && mCurrentHeight != maxHeight){
                mChild.postDelayed(this, 16);
            }
        }

    }


}

使所选项目更大Listview Android

1 个答案: