android开发心得(转载)

android开发经验(转载)

前言

?这里积累了一些不常见确又很实用的代码，每收集7条更新一次，希望能对大家有用。

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正文?

1、精确获取屏幕尺寸（例如：3.5、4.0、5.0寸屏幕）?

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? ??public?static?double?getScreenPhysicalSize(Activity?ctx)?{
????????DisplayMetrics?dm?=?new?DisplayMetrics();
????????ctx.getWindowManager().getDefaultDisplay().getMetrics(dm);
????????double?diagonalPixels?=?Math.sqrt(Math.pow(dm.widthPixels,?2)?+?Math.pow(dm.heightPixels,?2));
????????return?diagonalPixels?/?(160?*?dm.density);
????}

?一般是7寸以上是平板

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2、判断是否是平板（官方用法）

? ??public?static?boolean?isTablet(Context?context)?{
????????return?(context.getResources().getConfiguration().screenLayout?&?Configuration.SCREENLAYOUT_SIZE_MASK)?>=?Configuration.SCREENLAYOUT_SIZE_LARGE;
????}

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3、文字根据状态更改颜色?android:textColor?

<selector?xmlns:android="http://schemas.android.com/apk/res/android">
????<item?android:color="#53c1bd"?android:state_selected="true"/>
????<item?android:color="#53c1bd"?android:state_focused="true"/>
????<item?android:color="#53c1bd"?android:state_pressed="true"/>
????<item?android:color="#777777"/>
</selector>

??放在res/color/目录下

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4、背景色根据状态更改颜色 android:backgroup

<selector?xmlns:android="http://schemas.android.com/apk/res/android">

????<item?android:state_selected="true"><shape>

????????????<gradient?android:angle="0"?android:centerColor="#00a59f"?android:endColor="#00a59f"?android:startColor="#00a59f"?/>
????????</shape></item>
????<item?android:state_focused="true"><shape>
????????????<gradient?android:angle="0"?android:centerColor="#00a59f"?android:endColor="#00a59f"?android:startColor="#00a59f"?/>
????????</shape></item>
????<item?android:state_pressed="true"><shape>
????????????<gradient?android:angle="0"?android:centerColor="#00a59f"?android:endColor="#00a59f"?android:startColor="#00a59f"?/>
????????</shape></item>
????<item><shape>
????????????<gradient?android:angle="0"?android:centerColor="#00ff00"?android:endColor="00ff00"?android:startColor="00ff00"?/>
????????</shape></item>

</selector>

?如果直接给背景色color会报错。

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5、启动APK的默认Activity

? ??public?static?void?startApkActivity(final?Context?ctx,?String?packageName)?{
????????PackageManager?pm?=?ctx.getPackageManager();
????????PackageInfo?pi;
????????try?{
????????????pi?=?pm.getPackageInfo(packageName,?0);
????????????Intent?intent?=?new?Intent(Intent.ACTION_MAIN,?null);
????????????intent.addCategory(Intent.CATEGORY_LAUNCHER);
????????????intent.setPackage(pi.packageName);

????????????List<ResolveInfo>?apps?=?pm.queryIntentActivities(intent,?0);

????????????ResolveInfo?ri?=?apps.iterator().next();
????????????if?(ri?!=?null)?{
????????????????String?className?=?ri.activityInfo.name;
????????????????intent.setComponent(new?ComponentName(packageName,?className));
????????????????ctx.startActivity(intent);
????????????}
????????}?catch?(NameNotFoundException?e)?{
????????????Log.e("startActivity",?e);
????????}
????}

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7、计算字宽

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? ??public?static?float?GetTextWidth(String text,?float?Size)?{
????????TextPaint?FontPaint?=?new?TextPaint();
????????FontPaint.setTextSize(Size);
????????return?FontPaint.measureText(text);
????}

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注意如果设置了textStyle，还需要进一步设置TextPaint。?

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