Android Studio 上的 startB.setVisibility(View.VISIBLE) 崩溃

Question

尝试在进度条达到最大值 (100%) 后显示按钮，但应用程序由于某种原因崩溃。我可以让它改变颜色并在进度条加载后使其不可见，但由于某种原因不可见，请帮忙！

这是class.java代码：

int progress = 0;
ProgressBar simpleProgressBar;
Button startB = null;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_enteredring_page);
    // initiate progress bar and start button
    simpleProgressBar = (ProgressBar) findViewById(R.id.loadingfightbar);
    setProgressValue(progress);

    startB  = (Button)findViewById(R.id.showfight);
  //  startB.setVisibility(View.VISIBLE);


    View overlay = findViewById(R.id.inringlayout);

    overlay.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
            | View.SYSTEM_UI_FLAG_FULLSCREEN
            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);


    VideoView mVideoView = (VideoView) findViewById(R.id.videoView);
    String uriPath = "android.resource://com.seth.boxingadventure.boxerapp/" + R.raw.hayahadvid;
    Uri uri = Uri.parse(uriPath);
    mVideoView.setVideoURI(uri);
    mVideoView.requestFocus();
    mVideoView.start();



}

private void setProgressValue(final int progress) {

    // set the progress
    simpleProgressBar.setProgress(progress);

    // thread is used to change the progress value
    Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);

                if(simpleProgressBar.getProgress() == simpleProgressBar.getMax())
                {
                   // startB.setVisibility(View.VISIBLE);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            setProgressValue(progress + 10);


        }
    });
    thread.start();

}

}

还有xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:orientation="vertical"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="@android:color/white"
     android:id="@+id/inringlayout"
     android:weightSum="1">


<VideoView
    android:id="@+id/videoView"
    android:layout_width="fill_parent"
    android:layout_height="318dp"
    android:layout_weight="0.87" />

<ProgressBar
    android:id="@+id/loadingfightbar"
    style="?android:attr/progressBarStyleHorizontal"
    android:layout_width="300dp"
    android:layout_height="wrap_content"

    android:angle="270"
    android:centerColor="#C27452"
    android:centerY="0.75"
    android:endColor="#050505"


    android:startColor="#F0500A"
    android:visibility="visible"
    tools:visibility="visible"
    android:layout_below="@+id/videoView"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="81dp"

    android:max="100"
    android:progress="50"
    />

<Button
    android:id="@+id/showfight"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:visibility="invisible"
    android:layout_marginBottom="17dp" />

Answer 1

在 Android 中，主线程（UI 线程）只能访问 UI 组件，即您不能从非 UI 线程更改 UI 元素，如果您想从后台线程访问 UI 组件，请使用 runOnUiThread。
试试下面的代码：

    private void setProgressValue(final int progress) {

        // set the progress
        simpleProgressBar.setProgress(progress);

        // thread is used to change the progress value
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);

                    if(simpleProgressBar.getProgress() == simpleProgressBar.getMax())
                    {
                         runOnUiThread(new Runnable() {
                                        @Override
                                        public void run() {
                                           startB.setVisibility(View.VISIBLE);
                                        }
                                    });

                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                setProgressValue(progress + 10);


            }
        });
        thread.start();

    }

Answer 2

在android中，只有UI/主线程可以更新任何UI组件，所以你不能从后台线程更新UI，会导致崩溃

Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);

                if(simpleProgressBar.getProgress() == simpleProgressBar.getMax())
                {
                   // startB.setVisibility(View.VISIBLE);
                  // ^^^^^^^^^^^^^^^^^^ crash
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            setProgressValue(progress + 10);


        }
    });

解决方案：使用AsynchTask 或Handler or runOnUiThread

Answer 3

使用 runOnUiThread 像：

private void setProgressValue(final int progress) {

    // set the progress
    simpleProgressBar.setProgress(progress);

    // thread is used to change the progress value
    Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);

                if(simpleProgressBar.getProgress() == simpleProgressBar.getMax()) {
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            startB.setVisibility(View.VISIBLE);
                        }
                    });
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            setProgressValue(progress + 10);
        }
    });
    thread.start();
}