屏幕适配-像素密度

屏幕适配-像素密度

原理：修改density,scaleDensity,densityDpi值，直接更改系统内部对于目标尺寸而已言的像素密度。

density：表示像素密度 换句话说每一英寸像素的缩放比例 density = dpi / 160
scaleDenstiy: 表示字体的缩放比例，默认情况下和density是一致的
densityDpi：表示每一英寸共有多少个像素点 dpi=density*160

public class Density {

    private static final float WIDTH = 320;//参考设备的宽，单位是dp 320 / 2 = 160

    private static float appDensity;//表示屏幕密度
    private static float appScaleDensity; //字体缩放比例，默认appDensity

    public static void setDensity(final Application application, Activity activity) {
        //获取当前app的屏幕显示信息
        DisplayMetrics displayMetrics = application.getResources().getDisplayMetrics();
        if (appDensity == 0) {
            //初始化赋值操作
            appDensity = displayMetrics.density;
            appScaleDensity = displayMetrics.scaledDensity;

            //添加字体变化监听回调
            application.registerComponentCallbacks(new ComponentCallbacks() {
                @Override
                public void onConfigurationChanged(Configuration newConfig) {
                    //字体发生更改，重新对scaleDensity进行赋值
                    if (newConfig != null && newConfig.fontScale > 0) {
                        appScaleDensity = application.getResources().getDisplayMetrics().scaledDensity;
                    }
                }

                @Override
                public void onLowMemory() {

                }
            });
        }

        //计算目标值density, scaleDensity, densityDpi
        float targetDensity = displayMetrics.widthPixels / WIDTH; // 1080 / 360 = 3.0
        float targetScaleDensity = targetDensity * (appScaleDensity / appDensity);
        int targetDensityDpi = (int) (targetDensity * 160);

        //替换Activity的density, scaleDensity, densityDpi
        DisplayMetrics dm = activity.getResources().getDisplayMetrics();
        dm.density = targetDensity;
        dm.scaledDensity = targetScaleDensity;
        dm.densityDpi = targetDensityDpi;
    }

}

在Application进行设置，就不用在每个activity中设置了。

public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
                Density.setDensity(App.this, activity);
            }

            @Override
            public void onActivityStarted(Activity activity) {

            }

            @Override
            public void onActivityResumed(Activity activity) {

            }

            @Override
            public void onActivityPaused(Activity activity) {

            }

            @Override
            public void onActivityStopped(Activity activity) {

            }

            @Override
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

            }

            @Override
            public void onActivityDestroyed(Activity activity) {

            }
        });

    }
}