Question

我有类似的布局。

XML

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/mylayout" > </RelativeLayout>

java - 然后您可以使用以下代码动态更改布局的背景

public class MainActivity extends Activity {

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

        RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.mylayout);
        int images[] = {R.drawable.image1, R.drawable.image2, R.drawable.image3, R.drawable.image4};

        relativeLayout.setBackgroundResource(images[getRandomNumber()]);
         private Timer myTimer;
         myTimer = new Timer();
         myTimer.schedule(new TimerTask() 
         {          
            @Override
            public void run() 
            {
                TimerMethod();
            }
         }, 0, 9000);
    }

private void TimerMethod()
           {
               new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {

                    //TODO after 9 sec
                     relativeLayout.setBackgroundResource(images[getRandomNumber()]);
                }
            }, 9000);
        }
}

这是日志跟踪

01-04 01:08:15.307: E/AndroidRuntime(30200): FATAL EXCEPTION: Timer-0
01-04 01:08:15.307: E/AndroidRuntime(30200): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
01-04 01:08:15.307: E/AndroidRuntime(30200):    at android.os.Handler.<init>(Handler.java:121)
01-04 01:08:15.307: E/AndroidRuntime(30200):    at info.androidhive.slidingmenu.LoginActivity.TimerMethod(LoginActivity.java:55)
01-04 01:08:15.307: E/AndroidRuntime(30200):    at info.androidhive.slidingmenu.LoginActivity.access$0(LoginActivity.java:53)
01-04 01:08:15.307: E/AndroidRuntime(30200):    at info.androidhive.slidingmenu.LoginActivity$1.run(LoginActivity.java:48)
01-04 01:08:15.307: E/AndroidRuntime(30200):    at java.util.Timer$TimerImpl.run(Timer.java:284)

我想尝试的是在活动时自动更改它。

Answer 1

首次打开活动时，

onCreate()仅被调用一次。离开后，调用onPause()，稍后当您返回活动时，会调用onResume()。

因此，要在每次导航到“活动”时更改背景，请转换代码以将背景从onCreate()更改为onResume()。

public class MainActivity extends Activity {
RelativeLayout relativeLayout;
int images[];
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    relativeLayout = (RelativeLayout) findViewById(R.id.mylayout);
    images[]  = {R.drawable.image1, R.drawable.image2, R.drawable.image3, R.drawable.image4};     
}

protected void onResume()
{
    if(relativeLayout != null)
      relativeLayout.setBackgroundResource(images[getRandomNumber()]);

}

private int getRandomNumber() {
    //Note that general syntax is Random().nextInt(n)
    //It results in range 0-4
    //So it should be equal to number of images in images[] array
    return new Random().nextInt(4);
}}

Answer 2

您可以使用Timers和Handlers来完成此操作试试这段代码：

   public class MainActivity extends Activity {

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

        RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.mylayout);
        int images[] = {R.drawable.image1, R.drawable.image2, R.drawable.image3, R.drawable.image4};

        relativeLayout.setBackgroundResource(images[getRandomNumber()]);
         private Timer myTimer;
         myTimer = new Timer();
         myTimer.schedule(new TimerTask() 
         {          
            @Override
            public void run() 
            {
                TimerMethod();
            }
         }, 0, 9000);
    }

private void TimerMethod()
           {
               new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {

                    //TODO after 9 sec
                     relativeLayout.setBackgroundResource(images[getRandomNumber()]);
                }
            }, 9000);
        }
}

Answer 3

尝试拨打relativeLayout.setBackgroundResource(images[getRandomNumber()]); 在您的活动onResume()这样的方法上。

protected void onResume()
{
    if(relativeLayout != null){
          relativeLayout.setBackgroundResource(images[getRandomNumber()]);
    }
}

希望这有帮助。

Answer 4

在onCreate方法中，您的代码只会执行一次，如果您希望在一段时间间隔后更改代码，请使用TimerTask，或者也可以使用Handler。

Answer 5

首先在drawable res中创建transition_drawable.xml

<transition xmlns:android="http://schemas.android.com/apk/res/android">
 <item android:drawable="@drawable/one"/>
 <item android:drawable="@drawable/two"/>
 <item android:drawable="@drawable/three"/>

`

并在你的布局中

android:background="@drawable/transition_drawable"

并在您的activity.java中

int DrawableImage[] = {R.drawable.one , R.drawable.two, R.drawable.three};
final Handler handler = new Handler();
    final int[] i = {0};
    final int[] j = {1};
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Resources res = getApplicationContext().getResources();
                    TransitionDrawable out = new TransitionDrawable(new Drawable[]{res.getDrawable(DrawableImage[i[0]]), res.getDrawable(DrawableImage[j[0]])});
                    out.setCrossFadeEnabled(true);
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                        yourlayout.setBackground(out);
                    }
                    out.startTransition(2000);
                    i[0]++;
                    j[0]++;
                    if (j[0] == DrawableImage.length) {
                        j[0] = 0;
                    }
                    if (i[0] == DrawableImage.length) {
                        i[0] = 0;
                    }
                    handler.postDelayed(this, 4000);
                }
            });
        }
    }, 0);

Answer 6

我使它像这样工作：

private int[] backgroundImages = {R.drawable.bg1, R.drawable.bg2, R.drawable.bg3, R.drawable.bg4};
RelativeLayout background = findViewById(R.id.background);
background.setBackgroundResource(backgroundImages[new Random().nextInt(4)]);
Timer timer = new Timer();
    timer.schedule(new TimerTask() {
        @Override
        public void run() {
            new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
                @Override
                public void run() {
                    background.setBackgroundResource(backgroundImages[new Random().nextInt(4)]);
                }
            }, 3000);
        }
    }, 0, 3000);

Answer 7

我知道这个老问题，但是我会把我的答案发布给其他人，您可以使用以下代码

public class myActivity extends AppCompatActivity {

    RelativeLayout relativeLayout;
    int images[];

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

        relativeLayout = (RelativeLayout) findViewById(R.id.mylayout);
        images  = new int[{R.drawable.fighter3,R.drawable.sky,R.drawable.yellow_bullet,R.drawable.chicken3};

        //Create the timer object which will run the desired operation on a schedule or at a given time
        Timer timer = new Timer();

        //Create a task which the timer will execute.  This should be an implementation of the TimerTask interface.
        //I have created an inner class below which fits the bill.
        MyTimer mt = new MyTimer();

        //We schedule the timer task to run after 1000 ms and continue to run every 1000 ms.
        timer.schedule(mt, 1000, 1000);

    }

    private int getRandomNumber() {
        //Note that general syntax is Random().nextInt(n)
        //It results in range 0-4
        //So it should be equal to number of images in images[] array
        return new Random().nextInt(4);
    }

    class MyTimer extends TimerTask {

        public void run() {

            //This runs in a background thread.
            //We cannot call the UI from this thread, so we must call the main UI thread and pass a runnable
            runOnUiThread(new Runnable() {

                public void run() {
                    Random rand = new Random();
                    //The random generator creates values between [0,256) for use as RGB values used below to create a random color
                    //We call the RelativeLayout object and we change the color.  The first parameter in argb() is the alpha.
                    relativeLayout.setBackgroundResource(images[getRandomNumber()]);
                }
            });
        }
    }
}

动态自动更改布局背景

7 个答案: