我尝试设置IV_status.setImageResource(R.drawable.red)
但它似乎不起作用，每当调用上述代码时，整个应用程序
会崩溃。我也试过setBackgroundResource(R.drawable.red)但同样的问题是
正在发生。它在进入活动屏幕之前就崩溃了。
public class PhotosActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://10.0.8.41/pos/get_all_products.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "tables";
private static final String TAG_PID = "tableID";
private static final String TAG_NAME = "tableName";
private static final String TAG_AREA = "area";
private static final String TAG_STATUS = "status";
static ImageView IV_status;
// products JSONArray
JSONArray products = null;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.photos_layout);
IV_status = (ImageView) findViewById(R.id.status);
IV_status.setImageResource(R.drawable.red);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
}
// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(PhotosActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
products = json.getJSONArray(TAG_PRODUCTS);
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String area = c.getString(TAG_AREA);
String status = c.getString(TAG_STATUS);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
map.put(TAG_AREA,area);
map.put(TAG_STATUS, status);
// adding HashList to ArrayList
if(area.equals("A")){
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),PhotosActivity.class);// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
PhotosActivity.this, productsList,R.layout.list_item, new String[] { TAG_PID,TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<!-- Product id (pid) - will be HIDDEN - used to pass to other activity -->
<TextView
android:id="@+id/pid"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:visibility="gone" />
<!-- Name Label -->
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="20dip"
android:paddingLeft="6dip"
android:textSize="25dip"
android:textStyle="bold"
android:layout_weight="0.5"
/>
<ImageView
android:id="@+id/status"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"
android:layout_weight="0.5"/>
</LinearLayout>
使用堆栈跟踪记录：
07-26 05:50:49.379: D/dalvikvm(3118): GC_FOR_ALLOC freed 41K, 7% free 2614K/2804K, paused 33ms, total 37ms
07-26 05:50:49.464: D/AndroidRuntime(3118): Shutting down VM
07-26 05:50:49.464: W/dalvikvm(3118): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
07-26 05:50:49.480: E/AndroidRuntime(3118): FATAL EXCEPTION: main
07-26 05:50:49.480: E/AndroidRuntime(3118): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tabhost/com.example.tabhost.AndroidTabLayoutActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tabhost/com.example.tabhost.PhotosActivity}: java.lang.NullPointerException
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.os.Handler.dispatchMessage(Handler.java:99)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.os.Looper.loop(Looper.java:137)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-26 05:50:49.480: E/AndroidRuntime(3118): at java.lang.reflect.Method.invokeNative(Native Method)
07-26 05:50:49.480: E/AndroidRuntime(3118): at java.lang.reflect.Method.invoke(Method.java:511)
07-26 05:50:49.480: E/AndroidRuntime(3118): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-26 05:50:49.480: E/AndroidRuntime(3118): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-26 05:50:49.480: E/AndroidRuntime(3118): at dalvik.system.NativeStart.main(Native Method)
07-26 05:50:49.480: E/AndroidRuntime(3118): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tabhost/com.example.tabhost.PhotosActivity}: java.lang.NullPointerException
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.startActivityNow(ActivityThread.java:2023)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:749)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.widget.TabHost.setCurrentTab(TabHost.java:413)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.widget.TabHost.addTab(TabHost.java:240)
07-26 05:50:49.480: E/AndroidRuntime(3118): at com.example.tabhost.AndroidTabLayoutActivity.onCreate(AndroidTabLayoutActivity.java:40)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.Activity.performCreate(Activity.java:5104)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-26 05:50:49.480: E/AndroidRuntime(3118): ... 11 more
07-26 05:50:49.480: E/AndroidRuntime(3118): Caused by: java.lang.NullPointerException
07-26 05:50:49.480: E/AndroidRuntime(3118): at com.example.tabhost.PhotosActivity.onCreate(PhotosActivity.java:54)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.Activity.performCreate(Activity.java:5104)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-26 05:50:49.480: E/AndroidRuntime(3118): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-26 05:50:49.480: E/AndroidRuntime(3118): ... 21 more
07-26 05:50:49.722: D/dalvikvm(3118): GC_CONCURRENT freed 174K, 11% free 2860K/3180K, paused 128ms+41ms, total 246ms
列表显示
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>