先上ListView滑動改變標題欄背景漸變效果圖,透明轉變成不透明效果:
圖1:

圖2:

圖3:

圖4:

我用的是小米Note手機,狀態欄高度是55px,后面會提到,這里先做個說明:

下面的內容包含了所有代碼和一些測試數據:
代碼:
代碼很簡單,也做了注釋,這里就不廢話了。
先來布局文件:
activity的布局
activity_main_10
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <ListView android:id="@+id/listvew" android:layout_width="match_parent" android:layout_height="match_parent"/> <!--標題欄,這里簡單寫個textview--> <TextView android:id="@+id/title_tv" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="#00000000" android:gravity="center" android:orientation="vertical" android:padding="5dp" android:textSize="30sp"/></RelativeLayout>
listView頭布局
head_layout
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <ImageView android:id="@+id/head_iv" android:layout_width="match_parent" android:layout_height="150dp" android:background="@mipmap/ch"/></LinearLayout>
listView的item布局
listview_item_layout
<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="50dp"> <TextView android:id="@+id/item_tv" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:textSize="15sp"> </TextView></FrameLayout>
功能代碼:
MainActivity10
import android.app.Activity;import android.content.Context;import android.os.Bundle;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.AbsListView;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.ListView;import android.widget.TextView;import java.util.ArrayList;public class MainActivity10 extends Activity { private TextView title_tv; private ListView listvew; //listView的頭 private View headView; //listView頭中包含的布局。這里僅僅是一個ImageView private ImageView head_iv; private ArrayList<String> dataList; private MyAdapter myAdapter; //listview的頭部(這里是ImageView)頂部距離屏幕頂部(包含狀態欄)的距離 //注:這個高度,是頭布局在屏幕里才會計算的,出了屏幕,就不會變了 private int height; //listView的頭部的真實高度。頭布局的整體高度,因為這個demo只簡單寫了個ImageView作為頭部,所以ImageView的高度,就是頭部的高度 private int headViewHeight; private Context context; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main_10); context = this; title_tv = (TextView) findViewById(R.id.title_tv); listvew = (ListView) findViewById(R.id.listvew); headView = LayoutInflater.from(this).inflate(R.layout.head_layout, null); head_iv = (ImageView) headView.findViewById(R.id.head_iv); //添加listView的頭布局 listvew.addHeaderView(headView); dataList = new ArrayList<>(); for (int i = 0; i < 50; i++) { dataList.add("==" + i + "=="); } myAdapter = new MyAdapter(); listvew.setAdapter(myAdapter); listvew.setOnScrollListener(new AbsListView.OnScrollListener() { @Override public void onScrollStateChanged(AbsListView view, int scrollState) { } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { int location[] = new int[2]; /** * public void getLocationInWindow(@Size(2) int[] location) * * <p>Computes 計算 the coordinates 坐標 of this view in its window. The argument 參數 * must be an array of two integers. After the method returns, the array * contains 包含 the x and y location in that order.</p> * * @param location an array of two integers in which to hold the coordinates */ head_iv.getLocationInWindow(location); //listview的頭部(這里是ImageView)頂部距離屏幕頂部(包含狀態欄)的距離 height = location[1]; headViewHeight = head_iv.getHeight(); Utils.printLogData("==location==0==" + location[0]); Utils.printLogData("==location==1==" + location[1]); Utils.printLogData("==height==" + height); Utils.printLogData("==headViewHeight==" + headViewHeight); //在head_layout.xml中,固定設置了150dp的高度,用于和上面測量的對比 Utils.printLogData("==setHeigth==" + dip2px(150)); handleTitleBarColorEvaluate(); } }); } // 處理標題欄顏色漸變 private void handleTitleBarColorEvaluate() { //比例 float fraction; if (height > 0) { fraction = 1f - height * 1f / 60; if (fraction < 0f) { fraction = 0f; } title_tv.setAlpha(fraction); return; } //高度值是負數,但是負號僅僅是表示方向,取絕對值 float space = Math.abs(height) * 1f; // 標題欄的高度 fraction = space / headViewHeight; if (fraction < 0f) fraction = 0f; if (fraction > 1f) fraction = 1f; title_tv.setAlpha(1f); if (fraction >= 1f) { title_tv.setBackgroundColor(0xffec434b); } else { //根據比例,生成一個按比例的顏色值 title_tv.setBackgroundColor(ChenColorUtils.getNewColorByStartEndColor(context, fraction, R.color.transparent, R.color.red)); } if (fraction >= 0.8f) { title_tv.setTextColor(ChenColorUtils.getNewColorByStartEndColor(context, fraction, R.color.transparent, R.color.black)); title_tv.setText("標題欄"); } else { title_tv.setText(""); } } private class MyAdapter extends BaseAdapter { @Override public int getCount() { return dataList.size(); } @Override public Object getItem(int position) { return null; } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = LayoutInflater.from(context).inflate(R.layout.listview_item_layout, null); holder = new ViewHolder(); holder.item_tv = (TextView) convertView.findViewById(R.id.item_tv); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.item_tv.setText(dataList.get(position)); return convertView; } private class ViewHolder { private TextView item_tv; } } /** * dip轉換px */ public int dip2px(int dip) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (dip * scale + 0.5f); }}顏色:
colors.xml中添加
<color name="red">#ec434b</color><color name="transparent">#00000000</color><color name="black">#FF000000</color>
工具類代碼:
打印日志工具:
import android.util.Log;public class Utils { public static void printLogData(String data) { Log.e("chen", data); }}顏色工具:
import android.content.Context;public class ChenColorUtils { // 成新的顏色值 public static int getNewColorByStartEndColor(Context context, float fraction, int startValue, int endValue) { return evaluate(fraction, context.getResources().getColor(startValue), context.getResources().getColor(endValue)); } /** * 成新的顏色值 * @param fraction 顏色取值的級別 (0.0f ~ 1.0f) * @param startValue 開始顯示的顏色 * @param endValue 結束顯示的顏色 * @return 返回生成新的顏色值 */ public static int evaluate(float fraction, int startValue, int endValue) { int startA = (startValue >> 24) & 0xff; int startR = (startValue >> 16) & 0xff; int startG = (startValue >> 8) & 0xff; int startB = startValue & 0xff; int endA = (endValue >> 24) & 0xff; int endR = (endValue >> 16) & 0xff; int endG = (endValue >> 8) & 0xff; int endB = endValue & 0xff; return ((startA + (int) (fraction * (endA - startA))) << 24) | ((startR + (int) (fraction * (endR - startR))) << 16) | ((startG + (int) (fraction * (endG - startG))) << 8) | ((startB + (int) (fraction * (endB - startB)))); }}測試數據:
界面剛啟動
05-18 16:19:25.386 18718-18718/com.chen E/chen: ==location==0==0
05-18 16:19:25.387 18718-18718/com.chen E/chen: ==location==1==0
05-18 16:19:25.387 18718-18718/com.chen E/chen: ==height==0
05-18 16:19:25.387 18718-18718/com.chen E/chen: ==headViewHeight==0
05-18 16:19:25.387 18718-18718/com.chen E/chen: ==setHeigth==413
從時間上看,啟動約150毫秒(0.15秒)后
05-18 16:19:25.531 18718-18718/com.chen E/chen: ==location==0==0
05-18 16:19:25.531 18718-18718/com.chen E/chen: ==location==1==55
05-18 16:19:25.531 18718-18718/com.chen E/chen: ==height==55
05-18 16:19:25.531 18718-18718/com.chen E/chen: ==headViewHeight==413
05-18 16:19:25.531 18718-18718/com.chen E/chen: ==setHeigth==413
小米note,狀態欄高度是55像素。所以,一開始的時候,圖片距離屏幕頂部的高度就是55
向上滑動,當頭布局完全出到屏幕外面后,繼續滑動,打印數據不會變。
即:頭布局頂部距離屏幕頂部的高度(距離)不變。因為這個高度,只會在view在屏幕中才能獲取到。
詳見注釋
05-18 17:01:02.151 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.167 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.200 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.233 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.316 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.332 16873-16873/com.chen E/chen: ==height==-412
05-18 17:01:02.349 16873-16873/com.chen E/chen: ==height==-412
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