Question

我的代码如下，但是......当我运行它时，它什么都不做

Animation animation = new AlphaAnimation(1, 0); // Change alpha
// from fully
// visible to
// invisible
animation.setDuration(500); // duration - half a second
animation.setInterpolator(new LinearInterpolator()); // do not alter
// animation
// rate
animation.setRepeatCount(Animation.INFINITE); // Repeat animation
// infinitely
animation.setRepeatMode(Animation.REVERSE); // Reverse animation at
        // the
// end so the layout will
// fade back in
LinearLayout x = (LinearLayout)findViewById(R.id.warning);
x.clearAnimation();

vipul mittal建议之后的logcat

12-11 20:08:18.477: E/AndroidRuntime(1571): FATAL EXCEPTION: main
12-11 20:08:18.477: E/AndroidRuntime(1571): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.NTS.standroid/com.NTS.standroid.Settings}: java.lang.NullPointerException
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.os.Looper.loop(Looper.java:130)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread.main(ActivityThread.java:3683)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at java.lang.reflect.Method.invokeNative(Native Method)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at java.lang.reflect.Method.invoke(Method.java:507)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at dalvik.system.NativeStart.main(Native Method)
12-11 20:08:18.477: E/AndroidRuntime(1571): Caused by: java.lang.NullPointerException
12-11 20:08:18.477: E/AndroidRuntime(1571):     at com.NTS.standroid.Settings.onCreate(Settings.java:35)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-11 20:08:18.477: E/AndroidRuntime(1571):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
12-11 20:08:18.477: E/AndroidRuntime(1571):     ... 11 more

请提出任何建议。

我想让我的背景在我按下按钮后不断闪烁

我当前的代码

}
    @SuppressLint("NewApi")
    public void tintBackground() {
        LinearLayout x = (LinearLayout)findViewById(R.id.warning);
        ColorDrawable[] color = { new ColorDrawable(Color.RED),
                new ColorDrawable(Color.WHITE) };
        TransitionDrawable trans = new TransitionDrawable(color);
        int sdk = android.os.Build.VERSION.SDK_INT;
        if (sdk < android.os.Build.VERSION_CODES.JELLY_BEAN) {
            x.setBackgroundDrawable(trans);
        } else {
            x.setBackground(trans);
        }
        trans.startTransition(2000); // do transition over 2 seconds

}

和xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" 
    android:layout="@+id/warning">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout="@+id/warning1"
        android:layout_marginTop="50dp"
        android:layout_marginLeft="100dp"
        android:background="@drawable/warning"
        />
</LinearLayout>

Answer 1

我使用以下代码为我的应用程序的背景着色，也许你可以反复使用它：

@SuppressLint("NewApi")
public void tintBackground() {
    View rootView = findViewById(android.R.id.content);
    ColorDrawable[] color = { new ColorDrawable(Color.RED),
            new ColorDrawable(Color.WHITE) };
    TransitionDrawable trans = new TransitionDrawable(color);
    int sdk = android.os.Build.VERSION.SDK_INT;
    if (sdk < android.os.Build.VERSION_CODES.JELLY_BEAN) {
        rootView.setBackgroundDrawable(trans);
    } else {
        rootView.setBackground(trans);
    }
    trans.startTransition(2000); // do transition over 2 seconds

}

Answer 2

您必须在linearlayout上开始动画：

    Animation animation = new AlphaAnimation(1, 0); // Change alpha
    // from fully
    // visible to
    // invisible
    animation.setDuration(500); // duration - half a second
    animation.setInterpolator(new LinearInterpolator()); // do not alter
    // animation
    // rate
    animation.setRepeatCount(Animation.INFINITE); // Repeat animation
    // infinitely
    animation.setRepeatMode(Animation.REVERSE); // Reverse animation at

    // the
    // end so the layout will
    // fade back in
    LinearLayout x = (LinearLayout)findViewById(R.id.warning);
    x.startAnimation(animation)//<-- start animation don't clear it

Answer 3

我已经用它来反复淡出和淡出视图：

    fadeIn = new AlphaAnimation(0.25f, 1);
    fadeIn.setInterpolator(new AccelerateInterpolator()); // add this
    fadeIn.setDuration(500);
    fadeIn.setFillAfter(true);
    fadeIn.setAnimationListener(new RepeatAnimationListener());

    fadeOut = new AlphaAnimation(1, 0.25f);
    fadeOut.setInterpolator(new DecelerateInterpolator()); // and this
    fadeOut.setDuration(500);
    fadeOut.setFillAfter(true);
    fadeOut.setAnimationListener(new RepeatAnimationListener());

private boolean currently_fadeOut;

private class RepeatAnimationListener implements AnimationListener {
    public void onAnimationEnd(Animation animation) {

        if (currently_fadeOut) {
            view.startAnimation(fadeIn);
            currently_fadeOut = false;
        } else {
            view.startAnimation(fadeOut);
            currently_fadeOut = true;
        }
    }

    public void onAnimationRepeat(Animation animation) {
    }

    public void onAnimationStart(Animation animation) {
    }
}

// automatically repeated because of RepeatAnimationListener 
view.startAnimation(fadeOut);

如何让我的背景不断闪现动画

3 个答案: