我正在制作一个应用程序，您可以在其中显示照片并显示它以及更改背景图像的外观。我的应用程序一直在崩溃，并想知道你们是否知道这个问题是什么。干杯
MainActivity：
package com.example.triptych4;
import java.io.File;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends Activity {
// label our logs "CameraApp3"
private static String logtag = "CameraApp3";
// tells us which camera to take a picture from
private static int TAKE_PICTURE = 1;
// empty variable to hold our image Uri once we store it
private Uri imageUri;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// look for the button we set in the view
Button cameraButton = (Button)
findViewById(R.id.button_camera);
// set a listener on the button
cameraButton.setOnClickListener(cameraListener);
}
// set a new listener
private OnClickListener cameraListener = new OnClickListener() {
public void onClick(View v) {
// open the camera and pass in the current view
takePhoto(v);
}
};
public void takePhoto(View v) {
// tell the phone we want to use the camera
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
// create a new temp file called pic.jpg in the "pictures" storage area of the phone
File photo = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "pic.jpg");
// take the return data and store it in the temp file "pic.jpg"
intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photo));
// stor the temp photo uri so we can find it later
imageUri = Uri.fromFile(photo);
// start the camera
startActivityForResult(intent, TAKE_PICTURE);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
// override the original activity result function
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// call the parent
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode) {
// if the requestCode was equal to our camera code (1) then...
case 1:
// if the user took a photo and selected the photo to use
if(resultCode == Activity.RESULT_OK) {
// get the image uri from earlier
Uri selectedImage = imageUri;
// notify any apps of any changes we make
getContentResolver().notifyChange(selectedImage, null);
// get the imageView we set in our view earlier
ImageButton imageButton = (ImageButton)findViewById(R.id.button_camera);
// create a content resolver object which will allow us to access the image file at the uri above
ContentResolver cr = getContentResolver();
// create an empty bitmap object
Bitmap bitmap;
try {
// get the bitmap from the image uri using the content resolver api to get the image
bitmap = android.provider.MediaStore.Images.Media.getBitmap(cr, selectedImage);
// set the bitmap to the image view
imageButton.setImageBitmap(bitmap);
// notify the user
Toast.makeText(MainActivity.this, selectedImage.toString(), Toast.LENGTH_LONG).show();
} catch(Exception e) {
// notify the user
Toast.makeText(MainActivity.this, "failed to load", Toast.LENGTH_LONG).show();
Log.e(logtag, e.toString());
}
}
}
}
}
MyAndroidAppActivity：
package com.example.triptych4;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.view.View;
import android.view.View.OnClickListener;
public class MyAndroidAppActivity extends Activity {
Button button;
ImageView image;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addListenerOnButton();
}
public void addListenerOnButton() {
image = (ImageView) findViewById(R.id.imageView1);
button = (Button) findViewById(R.id.btnChangeImage);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
image.setImageResource(R.drawable.android3d);
}
});
}
}
布局
<FrameLayout
android:layout_width="wrap_content"
android:layout_height="match_parent" >
</FrameLayout>
<ImageView
android:id="@+id/imageView1"
android:layout_width="match_parent"
android:layout_height="390dp"
android:layout_marginTop="-35dp"
android:src="@drawable/android" />
<ImageButton
android:id="@+id/button_camera"
android:layout_width="170dp"
android:layout_height="258dp"
android:layout_marginLeft="-352dp"
android:layout_marginTop="25dp"
android:background="@drawable/middle" />
<Button
android:id="@+id/btnChangeImage"
android:layout_width="160dp"
android:layout_height="34dp"
android:layout_marginLeft="-167dp"
android:text="Change Image" />
</LinearLayout>
清单：
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:screenOrientation="landscape">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
logcat的：
05-06 14:41:19.363: I/art(1335): Background sticky concurrent mark sweep GC freed 1722(89KB) AllocSpace objects, 0(0B) LOS objects, 0% free, 2MB/2MB, paused 1.335ms total 105.604ms
05-06 14:41:19.650: D/AndroidRuntime(1335): Shutting down VM
05-06 14:41:19.659: E/AndroidRuntime(1335): FATAL EXCEPTION: main
05-06 14:41:19.659: E/AndroidRuntime(1335): Process: com.example.triptych4, PID: 1335
05-06 14:41:19.659: E/AndroidRuntime(1335): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.triptych4/com.example.triptych4.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread.access$800(ActivityThread.java:144)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.os.Handler.dispatchMessage(Handler.java:102)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.os.Looper.loop(Looper.java:135)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread.main(ActivityThread.java:5221)
05-06 14:41:19.659: E/AndroidRuntime(1335): at java.lang.reflect.Method.invoke(Native Method)
05-06 14:41:19.659: E/AndroidRuntime(1335): at java.lang.reflect.Method.invoke(Method.java:372)
05-06 14:41:19.659: E/AndroidRuntime(1335): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
05-06 14:41:19.659: E/AndroidRuntime(1335): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-06 14:41:19.659: E/AndroidRuntime(1335): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:41:19.659: E/AndroidRuntime(1335): at com.example.triptych4.MainActivity.onCreate(MainActivity.java:37)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.Activity.performCreate(Activity.java:5933)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
05-06 14:41:19.659: E/AndroidRuntime(1335): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
05-06 14:41:19.659: E/AndroidRuntime(1335): ... 10 more
05-06 14:41:55.802: I/Process(1335): Sending signal. PID: 1335 SIG: 9
05-06 14:42:21.608: I/art(1378): Background partial concurrent mark sweep GC freed 117(17KB) AllocSpace objects, 0(0B) LOS objects, 25% free, 2MB/2MB, paused 11.483ms total 365.174ms
05-06 14:42:22.181: D/AndroidRuntime(1378): Shutting down VM
05-06 14:42:22.273: E/AndroidRuntime(1378): FATAL EXCEPTION: main
05-06 14:42:22.273: E/AndroidRuntime(1378): Process: com.example.triptych4, PID: 1378
05-06 14:42:22.273: E/AndroidRuntime(1378): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.triptych4/com.example.triptych4.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread.access$800(ActivityThread.java:144)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.os.Handler.dispatchMessage(Handler.java:102)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.os.Looper.loop(Looper.java:135)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread.main(ActivityThread.java:5221)
05-06 14:42:22.273: E/AndroidRuntime(1378): at java.lang.reflect.Method.invoke(Native Method)
05-06 14:42:22.273: E/AndroidRuntime(1378): at java.lang.reflect.Method.invoke(Method.java:372)
05-06 14:42:22.273: E/AndroidRuntime(1378): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
05-06 14:42:22.273: E/AndroidRuntime(1378): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-06 14:42:22.273: E/AndroidRuntime(1378): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:42:22.273: E/AndroidRuntime(1378): at com.example.triptych4.MainActivity.onCreate(MainActivity.java:37)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.Activity.performCreate(Activity.java:5933)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
05-06 14:42:22.273: E/AndroidRuntime(1378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
05-06 14:42:22.273: E/AndroidRuntime(1378): ... 10 more
05-06 14:47:24.069: I/Process(1378): Sending signal. PID: 1378 SIG: 9
05-06 14:50:00.607: I/art(1428): Background sticky concurrent mark sweep GC freed 1722(89KB) AllocSpace objects, 0(0B) LOS objects, 0% free, 2MB/2MB, paused 1.353ms total 189.333ms
05-06 14:50:00.742: D/AndroidRuntime(1428): Shutting down VM
05-06 14:50:00.755: E/AndroidRuntime(1428): FATAL EXCEPTION: main
05-06 14:50:00.755: E/AndroidRuntime(1428): Process: com.example.triptych4, PID: 1428
05-06 14:50:00.755: E/AndroidRuntime(1428): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.triptych4/com.example.triptych4.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread.access$800(ActivityThread.java:144)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.os.Handler.dispatchMessage(Handler.java:102)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.os.Looper.loop(Looper.java:135)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread.main(ActivityThread.java:5221)
05-06 14:50:00.755: E/AndroidRuntime(1428): at java.lang.reflect.Method.invoke(Native Method)
05-06 14:50:00.755: E/AndroidRuntime(1428): at java.lang.reflect.Method.invoke(Method.java:372)
05-06 14:50:00.755: E/AndroidRuntime(1428): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
05-06 14:50:00.755: E/AndroidRuntime(1428): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-06 14:50:00.755: E/AndroidRuntime(1428): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:50:00.755: E/AndroidRuntime(1428): at com.example.triptych4.MainActivity.onCreate(MainActivity.java:37)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.Activity.performCreate(Activity.java:5933)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
05-06 14:50:00.755: E/AndroidRuntime(1428): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
05-06 14:50:00.755: E/AndroidRuntime(1428): ... 10 more
05-06 14:50:08.090: I/Process(1428): Sending signal. PID: 1428 SIG: 9
05-06 14:50:31.291: I/art(1467): Background partial concurrent mark sweep GC freed 79(16KB) AllocSpace objects, 0(0B) LOS objects, 24% free, 2MB/2MB, paused 61.291ms total 133.616ms
05-06 14:50:31.352: D/AndroidRuntime(1467): Shutting down VM
05-06 14:50:31.363: E/AndroidRuntime(1467): FATAL EXCEPTION: main
05-06 14:50:31.363: E/AndroidRuntime(1467): Process: com.example.triptych4, PID: 1467
05-06 14:50:31.363: E/AndroidRuntime(1467): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.triptych4/com.example.triptych4.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread.access$800(ActivityThread.java:144)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.os.Handler.dispatchMessage(Handler.java:102)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.os.Looper.loop(Looper.java:135)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread.main(ActivityThread.java:5221)
05-06 14:50:31.363: E/AndroidRuntime(1467): at java.lang.reflect.Method.invoke(Native Method)
05-06 14:50:31.363: E/AndroidRuntime(1467): at java.lang.reflect.Method.invoke(Method.java:372)
05-06 14:50:31.363: E/AndroidRuntime(1467): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
05-06 14:50:31.363: E/AndroidRuntime(1467): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-06 14:50:31.363: E/AndroidRuntime(1467): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-06 14:50:31.363: E/AndroidRuntime(1467): at com.example.triptych4.MainActivity.onCreate(MainActivity.java:37)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.Activity.performCreate(Activity.java:5933)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
05-06 14:50:31.363: E/AndroidRuntime(1467): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
05-06 14:50:31.363: E/AndroidRuntime(1467): ... 10 more
答案 0 :(得分：0)
在您的Xml中，您有ImageButton。
<ImageButton
android:id="@+id/button_camera"
.... />
但是在您的MainActivity中，您将其用作Button。
Button cameraButton = (Button)
findViewById(R.id.button_camera);
将其更改为ImageButton。
ImageButton cameraButton = (ImageButton)
findViewById(R.id.button_camera);
答案 1 :(得分：0)
您尝试将ImageButton强制转换为Button，因此请替换此代码：
ImageButton cameraButton = (ImageButton) findViewById(R.id.button_camera);
答案 2 :(得分：0)
您正在将ImageButton cameraButton投射到Button。
使用
ImageButton cameraButton = (ImageButton)
findViewById(R.id.button_camera);
而不是
Button cameraButton = (Button)
findViewById(R.id.button_camera);