我有一个只使用ImageView切换屏幕的应用。我有两个按钮：上一个和下一个。这些按钮可浏览ImageView布局中的图像。我的下一步按钮工作得很好，但上一个按钮根本不起作用。它不会回到上一张图片。这是我的整个活动：
public class StanActivity extends Activity {
ImageView image;
Button next;
int a = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.stan_xml);
image = (ImageView) findViewById(R.id.imageView1);
next = (Button) findViewById(R.id.next);
next.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
// TODO Auto-generated method stub
switch (view.getId()) {
case R.id.next:
if (a == 0) {
image.setImageResource(R.drawable.stan1);
a = 1;
} else if (a == 1) {
image.setImageResource(R.drawable.stan2);
a = 2;
} else if (a == 2) {
image.setImageResource(R.drawable.stan3);
a = 3;
} else if (a == 3) {
image.setImageResource(R.drawable.stan4);
a = 4;
} else if (a == 4) {
image.setImageResource(R.drawable.stan5);
a = 5;
} else if (a == 5) {
image.setImageResource(R.drawable.stan6);
a = 6;
} else if (a == 6) {
image.setImageResource(R.drawable.stan7);
a = 7;
} else if (a == 7) {
image.setImageResource(R.drawable.stan8);
a = 8;
} else if (a == 8) {
image.setImageResource(R.drawable.finalstan);
a = 9;
next.setVisibility(View.GONE);
}
}
}
});
Button previous = (Button) findViewById(R.id.prev);
previous.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
// TODO Auto-generated method stub
switch (view.getId()) {
case R.id.prev:
a--;
next.performClick();
break;
}
}
});
}
}
感谢您的帮助。
更新代码：
public class StanActivity extends Activity {
public int currentImage = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.stan_xml);
final int[] images = new int[] { R.drawable.stan1, R.drawable.stan2,
R.drawable.stan3, R.drawable.stan4, R.drawable.stan5,
R.drawable.stan6, R.drawable.stan7, R.drawable.stan8 };
final ImageView image = (ImageView) findViewById(R.id.imageView1);
final Button next = (Button) findViewById(R.id.next);
final Button previous = (Button) findViewById(R.id.prev);
next.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
currentImage++;
if (currentImage >= images.length) {
currentImage = images.length;
next.setVisibility(View.GONE);
}
previous.setVisibility(View.VISIBLE);
image.setImageResource(images[currentImage]); /* ERROR IN THIS LINE */
}
});
previous.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
currentImage--;
if (currentImage <= 0) {
currentImage = 0;
previous.setVisibility(View.GONE);
}
next.setVisibility(View.VISIBLE);
image.setImageResource(images[currentImage]);
}
});
}
}
和LogCat：
11-21 22:16:18.101: D/dalvikvm(22524): GC_FOR_ALLOC freed 3193K, 12% free 61564K/69760K, paused 34ms, total 34ms
11-21 22:16:18.611: D/dalvikvm(22524): GC_FOR_ALLOC freed 3032K, 15% free 61512K/71660K, paused 21ms, total 21ms
11-21 22:16:18.611: I/dalvikvm-heap(22524): Grow heap (frag case) to 67.738MB for 2492416-byte allocation
11-21 22:16:19.341: D/dalvikvm(22524): GC_FOR_ALLOC freed 2979K, 17% free 61955K/74096K, paused 13ms, total 13ms
11-21 22:16:20.191: D/AndroidRuntime(22524): Shutting down VM
11-21 22:16:20.191: W/dalvikvm(22524): threadid=1: thread exiting with uncaught exception (group=0x417c5898)
11-21 22:16:20.191: E/AndroidRuntime(22524): FATAL EXCEPTION: main
11-21 22:16:20.191: E/AndroidRuntime(22524): java.lang.ArrayIndexOutOfBoundsException: length=8; index=8
11-21 22:16:20.191: E/AndroidRuntime(22524): at deimantasb.howtodrawsouthpark.StanActivity$1.onClick(StanActivity.java:37)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.view.View.performClick(View.java:4475)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.view.View$PerformClick.run(View.java:18784)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.os.Handler.handleCallback(Handler.java:730)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.os.Handler.dispatchMessage(Handler.java:92)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.os.Looper.loop(Looper.java:137)
11-21 22:16:20.191: E/AndroidRuntime(22524): at android.app.ActivityThread.main(ActivityThread.java:5414)
11-21 22:16:20.191: E/AndroidRuntime(22524): at java.lang.reflect.Method.invokeNative(Native Method)
11-21 22:16:20.191: E/AndroidRuntime(22524): at java.lang.reflect.Method.invoke(Method.java:525)
11-21 22:16:20.191: E/AndroidRuntime(22524): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
11-21 22:16:20.191: E/AndroidRuntime(22524): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
11-21 22:16:20.191: E/AndroidRuntime(22524): at dalvik.system.NativeStart.main(Native Method)
11-21 22:21:30.321: I/Process(22524): Sending signal. PID: 22524 SIG: 9
答案 0 :(得分：1)
您之前的按钮正在点击下一个按钮，这意味着它正在执行a = a - 1 + 1 = a。解决这个问题的一种愚蠢的方法是让前一个按钮返回两个（a - = 2;），然后点击下一个。
将所有资源放入数组可能更好： int [] images = new int [] {R.drawable.stan1，R.drawable.stan2，...}; 然后使用image.setImageResource（images [a]）;代替。
试试这个：
public class StanActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.stan_xml);
long[] images = new long[] {R.drawable.stan1, R.drawable.stan2, R.drawable.stan3 /* etc */};
int currentImage = 0;
ImageView image = (ImageView) findViewById(R.id.imageView1);
Button next = (Button) findViewById(R.id.next);
Button previous = (Button) findViewById(R.id.prev);
next.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
currentImage++;
if (currentImage >= images.length - 1) {
currentImage = images.length - 1;
next.setVisibility(View.GONE);
}
previous.setVisibility(View.VISIBLE);
image.setImageResource(images[currentImage]);
}
});
previous.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
currentImage--;
if (currentImage <= 0) {
currentImage = 0;
previous.setVisibility(VIEW.GONE);
}
next.setVisibility(View.VISIBLE);
image.setImageResource(images[currentImage]);
}
});
}
}
答案 1 :(得分：0)
使用a = a-2代替a--。或者像你下一次做的那样实现上一个按钮。