Android 开发笔记

Android

android开发过程中遇到的一些问题，应用场景，代码片段。有解决也有疑惑，一起探讨。。。…

1,PopupWindow消失的问题

在fragment中使用PopupWindow，点击它区域外的地方，让其自动隐藏。

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private PopupWindow popupWindow;
    private void showPopWindow() {
        if(popupWindow == null){
            View pop_view = activity.getLayoutInflater().inflate(R.layout.popwin_order_list, null);
            popupWindow = new PopupWindow(pop_view, UIUtils.dip2px(context,100),  RelativeLayout.LayoutParams.WRAP_CONTENT,true);
            initRadioButton(pop_view);
        }
        popupWindow.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        popupWindow.setOutsideTouchable(true);//该属性设置为true,则在点击屏幕的空白位置也会退出
        popupWindow.setFocusable(true);
        popupWindow.setTouchable(true);
        popupWindow.showAsDropDown(toolbar.getTvRight2(), -80, 0);
    }

2,FragmentTabHost切换其它fragment，后退crash

布局文件

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<android.support.v4.app.FragmentTabHost
        android:id="@android:id/tabhost"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0"
        android:background="@color/bottomTabBarColor">
        <FrameLayout
            android:id="@+id/fl_tab_wrap"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    </android.support.v4.app.FragmentTabHost>

代码初始化tabhost

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private void initTabHost() {
        layoutInflater = LayoutInflater.from(this);
        mTabHost = (FragmentTabHost)findViewById(android.R.id.tabhost);
        mTabHost.setup(this, getSupportFragmentManager(), R.id.fl_home_content);
        int count = mFragmentArray.length;
        for(int i = 0; i < count; i++){
            TabHost.TabSpec tabSpec = mTabHost.newTabSpec(context.getString(mTextviewArray[i])).setIndicator(getTabItemView(i));
            mTabHost.addTab(tabSpec, mFragmentArray[i], null);
            mTabHost.getTabWidget().setShowDividers((LinearLayout.SHOW_DIVIDER_NONE));
        }
    }
    private View getTabItemView(int index){
        View view = layoutInflater.inflate(R.layout.home_tab_item, null);
        ImageView imageView = (ImageView) view.findViewById(R.id.iv_tab_icon);
       imageView.setImageResource(mImageViewArray[index]);
        return view;
    }

如果，当某个fragment中切换其他fragment（不是tab对应的mFragmentArray中），返回就会crash。原因是什么？

3，对话框问题

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<!--自定义对话框-->
    <style name="dialog1" parent="@android:style/Theme.Dialog">
        <item name="android:windowFrame">@null</item><!--边框-->
        <item name="android:windowIsFloating">true</item><!--是否浮现在activity之上-->
        <item name="android:windowIsTranslucent">true</item><!--半透明-->
        <item name="android:windowNoTitle">true</item><!--无标题-->
        <item name="android:windowBackground">@android:color/darker_gray</item><!--背景透明-->
        <item name="android:backgroundDimEnabled">true</item><!--背景变暗-->
    </style>
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 public void showCommonDialog(final OnDialogBtnClickListener onDialogBtnClickListener) {
        final Dialog dialog = new Dialog(context, R.style.dialog1);
//自定义布局文件     dialog.setContentView(R.layout.dialog_common_hint);
        dialog.setCancelable(true);
        btn_left = (Button) dialog.findViewById(R.id.btn_positive);
        btnRight = (Button) dialog.findViewById(R.id.btn_negative);
        TextView tv_description = (TextView)dialog.findViewById(R.id.tv_dialog_description);
        tv_description.setText(description);
        //左侧
        btn_left.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onDialogBtnClickListener.onPositiveClick(v);
                dialog.dismiss();
            }
        });
        //右侧
        btnRight.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onDialogBtnClickListener.onNegativeClick(v);
                dialog.dismiss();
            }
        });
        dialog.show();
    }

dialog对应的布局，添加一个圆角背景

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<?xml version="1.0" encoding="utf-8"?>
<shape
  xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners android:radius="10dp" />
    <solid android:color="@color/common_bg" />
</shape>

4，水平进度条

1、新建 myprogress_style.xml在drawable中

android:startColor=”@color/red” 为自定义开始颜色

为两头圆角的弧度，值越大越圆

为设置渐变色背景 angle 为角度

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<?xml version="1.0" encoding="UTF-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@android:id/background">
	<shape>
	<corners android:radius="8.0dip" />
	<gradient android:startColor="#EEEEEE" android:endColor="#EEEEEE"
	android:angle="270.0" />
	</shape>
</item>
<item android:id="@android:id/progress">
	<clip>
	<shape>
		<corners android:radius="0.0dip" />
		<gradient android:startColor="@color/red" android:endColor="@color/red"
		android:centerColor="@color/red" android:angle="270.0" />
	</shape>
	</clip>
</item>
</layer-list>

2、应用样式

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<ProgressBar android:id="@+id/pic_ProgressBar"
style="?android:attr/progressBarStyleHorizontal" 
android:layout_width="fill_parent" 
android:visibility="gone" 
android:layout_height="5dip"
android:progressDrawable="@drawable/myprogress_style">

5，splash首屏加载黑屏问题

//设置透明Theme，防止黑白屏，进入app闪烁

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<style name="Theme.AppTranslucent" parent="android:Theme">  
    <item name="android:windowIsTranslucent">true</item> 
    <item name="android:windowNoTitle">true</item>  
</style>

6，物理后退模拟点击Home键

后退，直接返回桌面，并不退出应用。

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@Override
public void onBackPressed() {
    //super.onBackPressed();这句话要注掉,否则又去调用默认的back处理方式了
    Intent mIntent = new Intent();
    mIntent.setAction(Intent.ACTION_MAIN);
    mIntent.addCategory(Intent.CATEGORY_HOME);
    startActivity(mIntent);
}
``` java
### 7，根据android文件ID，查找缩略图
视频缩略图类似，通过多媒体数据库获取。
``` java
 private Bitmap getImageThumbBitmap(int ImageID, String path) {
        Bitmap bitmap = null;
        if (ImageID!=-1&&ImageID>0) {
            bitmap = MediaStore.Images.Thumbnails.getThumbnail(
                    contentResolver, ImageID, MediaStore.Images.Thumbnails.MINI_KIND, null);
        }
        if (bitmap == null){
            bitmap = MyFileUtils.getImageThumbnail(path, 80, 80);
        }
        return bitmap;
    }

8，string.xml中不能有特殊符号

项目中要在string.xml 中显示特殊符号，如@号冒号等，直接写肯定不行啦。使用ASCII码进行显示。如：

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@号 &#064; 
:号 &#058; 
空格 &#160;

9，Android自定义通知栏

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public void createNotification() {
        String title = context.getString(R.string.notify_downloading_title)+fileName;
        notification = new Notification(
                R.mipmap.ic_launcher,//应用的图标
                title,
                System.currentTimeMillis());
        notification.tickerText = title;
        //notification.flags = Notification.FLAG_ONGOING_EVENT;
        notification.flags = Notification.FLAG_AUTO_CANCEL;
        contentView = new RemoteViews(context.getPackageName(),R.layout.notification_item);
        contentView.setTextViewText(R.id.notificationTitle, title);
        contentView.setTextViewText(R.id.notificationPercent, "0%");
        contentView.setProgressBar(R.id.notificationProgress, 100, 0, false);
        notification.contentView = contentView;
        //点击后进入缓存列表
        downloadIntent = new Intent(context, HomeActivity.class);
        downloadIntent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(context, 0, downloadIntent, 0);
        notification.contentIntent = pendingIntent;
        notificationManager = NotificationUtils.getManager(context);
    }

10，Android常用工具，其他相关

IDE：android studio，eclipse
文本编辑器：Sublmine，Atom
版本控制：svn，git
笔记：为知笔记，有道云笔记，万象笔记
开发者学习常用站点：github，csdn，简书，掘金，推酷，慕课网
android大牛：一大堆，希望有你。

欢迎交流，未完待续！

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Dusan_杜乾：Q：291902259，公众号：OpenDeveloper