如何修复慢速渲染（Android维权） [英] How to fix Slow Rendering (Android vitals)

问题描述

我有一款应用在新版Google Play控制台 - 低延迟渲染的Android vitals部分中列为最低25％。我很担心这是因为

下面是从 systrace 中取得的两张图片，它演示了在1帧中在UI线程上运行的工作。最上面的是 layout_width = wrap_content ，最下面的是 layout_width = match_parent 。

我测试过的以下两种方法可以提高帧速率： b
$ b

• 如果你以16ms（ seekBar.postDelayed（runnable，16））的较短跨度发布runnable，您可以获得这种平滑的60fps：
  

  
  
  

  P / s：我不确定为什么。
  

• 使用其他方式更新 count 值，而不是在可运行。使用 View.postOnAnimation（Runnable）重新安排Runnable。样本项目的结果是60FPS。编辑：
  two Runnable 使用
  

$ b postOnAnimation（Runnable）

  Runnable runnable = 
 new Runnable （）{
 @Override 
 public void run（）{
 textView.setText（Integer.toString（count））; 
 seekBar.setProgress（count）; 
 seekBar.postOnAnimation（this）; 
} 
}; 
 
 
 
 Runnable updateCount = new Runnable（）{
 @Override public void run（）{
 ++ count; 
 seekBar.postDelayed（this，250）; 
} 
}; 
  

I have an app that is listed as in the bottom 25% in the new Google Play Console - Android vitals section for Slow Rendering. I am concerned of this because of such articles that seem to say Google Play may penalize your app in the Play Store rankings if you fall in the bottom 25%.

However, it seems impossible to improve this metric for my app. It plays music and has a SeekBar and TextView which is updated every 250ms as any music player would. I made the minimum basic program to demonstrate:

public class MainActivity extends AppCompatActivity {

    int count;
    SeekBar seekBar;
    TextView textView;

    Runnable runnable =
            new Runnable() {
                @Override
                public void run() {
                    textView.setText(Integer.toString(count));
                    seekBar.setProgress(count);
                    ++count;
                    seekBar.postDelayed(runnable, 250);
                }
            };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        seekBar = (SeekBar) findViewById(R.id.seek);
        textView = (TextView) findViewById(R.id.text);
        seekBar.post(runnable);
    }
}

Full project here: https://github.com/svenoaks/SlowRendering.git

When I run this program on hardware similar to the Nexus devices, I get these results for a
adb shell dumpsys gfxinfo com.example.xyz.slowrendering command:

Stats since: 19222191084749ns
Total frames rendered: 308
Janky frames: 290 (94.16%)
90th percentile: 32ms
95th percentile: 36ms
99th percentile: 44ms
Number Missed Vsync: 2
Number High input latency: 0
Number Slow UI thread: 139
Number Slow bitmap uploads: 0
Number Slow issue draw commands: 283

This would mean almost all my frames taking >16ms to render, I guess due to the periodic nature of the updating. All other music player apps I have tested also have this Slow Rendering problem as far as I can see. I fear Google's algorithm ruining my app ranking, is there any way I can improve my score?

解决方案

The TextView in your layout is causing the problem. Because it has layout width of wrap_content, which said that it's width has to be equals to the width of the content (the text in this example). Therefore, every time you call TextView.setText an expensive measure/layout pass has to occur. Simple setting the layout_width to match_parent will solve the issue.

Here are two images what is taken from systrace, it demonstrate the work run on the UI thread in 1 frame. The top one is done with layout_width=wrap_content and the bottom one is with layout_width=match_parent.

Two following methods that i have tested will improve the frame rate:

• If you post the runnable in shorter span like 16ms (seekBar.postDelayed(runnable, 16)), you get this smooth 60fps:

  P/s: I am not sure why yet.

• Use some other way to update the count value instead of inside the Runnable. Use View.postOnAnimation(Runnable) to reschedule the Runnable. The result is 60FPS for the sample project.

EDIT: two Runnable that uses postOnAnimation(Runnable)

Runnable runnable =
  new Runnable() {
    @Override
    public void run() {
      textView.setText(Integer.toString(count));
      seekBar.setProgress(count);
      seekBar.postOnAnimation(this);
    }
  };



Runnable updateCount = new Runnable() {
    @Override public void run() {
      ++count;
      seekBar.postDelayed(this, 250);
    }
  };

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