我正在尝试使用2个TextViews和1个Button创建一个ListView。当用户点击按钮时，活动将完成（）;并将结果传递给另一个视图。我跟着this tutorial 。但出于某种原因，当我点击开始该活动时，我的应用程序崩溃了！这是我的应用程序中的3个相关文件。
列表结构数据：
public class formulasListData {
private String formulasName;
private String formulasDefinition;
public formulasListData(String formulasName, String formulasDefinition) {
super();
this.formulasName = formulasName;
this.formulasDefinition = formulasDefinition;
}
public String getFormulasName() {
return formulasName;
}
public void setFormulasName(String formulasName) {
this.formulasName = formulasName;
}
public String getFormulasDefinition() {
return formulasDefinition;
}
public void setFormulasDefinition(String formulasDefinition) {
this.formulasDefinition = formulasDefinition;
}
}
列表适配器：
public class formulasListAdapter extends BaseAdapter implements OnClickListener {
private Context context;
private List<formulasListData> formulasList;
public formulasListAdapter(Context context, List<formulasListData> formulasList) {
this.context = context;
this.formulasList = formulasList;
}
@Override
public int getCount() {
return formulasList.size();
}
@Override
public Object getItem(int position) {
return formulasList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View rowView, ViewGroup parent) {
formulasListData entry = formulasList.get(position);
if(rowView == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
rowView = inflater.inflate(R.layout.formulas_row, null);
}
TextView formulasName = (TextView) rowView.findViewById(R.id.formulas_name);
formulasName.setText(entry.getFormulasName());
TextView formulasDefinition = (TextView) rowView.findViewById(R.id.formulas_definition);
formulasDefinition.setText(entry.getFormulasDefinition());
Button btnSelect = (Button) rowView.findViewById(R.id.selectFormula);
btnSelect.setFocusableInTouchMode(false);
btnSelect.setFocusable(false);
btnSelect.setOnClickListener(this);
btnSelect.setTag(entry);
return rowView;
}
@Override
public void onClick(View view) {
formulasListData entry = (formulasListData) view.getTag();
}
}
应显示列表的活动。
public class FormulasList extends Activity {
private static final int FORMULA_0 = 0;
private static final int FORMULA_1 = 1;
private static final int FORMULA_2 = 2;
private static final int FORMULA_3 = 3;
private static final int FORMULA_4 = 4;
private static final int FORMULA_5 = 5;
private static final int FORMULA_6 = 6;
// private static final int FORMULA_7 = 7;
public void onCreate(Bundle savedInstance) {
super.onCreate(savedInstance);
ListView formulasListView = (ListView) findViewById(R.id.formulas_list);
formulasListView.setClickable(true);
final List<formulasListData> formulasList = new ArrayList<formulasListData>();
final String[] formulasName = new String[] {"Circunference of a Circle:",
"Area of a Circle:",
"Volume of a Sphere:",
"Area Triangle:",
"Area Square:",
"Volume of a Cube:",
"Pithagorean Theorem:"};
final String[] formulasDefinition = new String[] {"2 × π × r",
"π × r²",
"(4/3) × π × r³",
"(b × h)/2",
"side²",
"side³",
"a² + b² = c²"};
// formulasList.add(new formulasListData(formulasName, formulasDefinition));
formulasList.add(new formulasListData(formulasName[0], formulasDefinition[0]));
formulasList.add(new formulasListData(formulasName[1], formulasDefinition[1]));
formulasList.add(new formulasListData(formulasName[2], formulasDefinition[2]));
formulasList.add(new formulasListData(formulasName[3], formulasDefinition[3]));
formulasList.add(new formulasListData(formulasName[4], formulasDefinition[4]));
formulasList.add(new formulasListData(formulasName[5], formulasDefinition[5]));
formulasList.add(new formulasListData(formulasName[6], formulasDefinition[6]));
SharedPreferences settings = getSharedPreferences(SettingsActivity.PREF_NAME, MODE_PRIVATE);
SettingsActivity.newTheme = settings.getInt("themeCustom", 0);
if(SettingsActivity.newTheme == SettingsActivity.THEME_DARK) {
setTheme(R.style.DarkTheme);
} else if(SettingsActivity.newTheme == SettingsActivity.THEME_LIGHT){
setTheme(R.style.LightTheme);
} else if(SettingsActivity.newTheme == SettingsActivity.THEME_COLORS) {
setTheme(R.style.ColorsTheme);
} else {
setTheme(R.style.AppTheme);
}
setContentView(R.layout.activity_formulas);
formulasListAdapter adapter = new formulasListAdapter(this, formulasList);
formulasListView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int position,long index) {
Intent intent= getIntent();
Bundle b = new Bundle();
switch (position) {
case FORMULA_0:
b.putString("key0", formulasDefinition[0]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_1:
b.putString("key0", formulasDefinition[1]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_2:
b.putString("key0", formulasDefinition[2]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_3:
b.putString("key0", formulasDefinition[3]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_4:
b.putString("key0", formulasDefinition[4]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_5:
b.putString("key0", formulasDefinition[5]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
case FORMULA_6:
b.putString("key0", formulasDefinition[6]);
intent.putExtras(b);
setResult(RESULT_OK, intent);
finish();
break;
default:
break;
}
}
});
formulasListView.setAdapter(adapter);
}
}
非常感谢!!
编辑：这是LogCat
05-01 20:06:54.436: D/libEGL(4820): loaded /system/lib/egl/libEGL_tegra.so
05-01 20:06:54.456: D/libEGL(4820): loaded /system/lib/egl/libGLESv1_CM_tegra.so
05-01 20:06:54.466: D/libEGL(4820): loaded /system/lib/egl/libGLESv2_tegra.so
05-01 20:06:54.486: D/OpenGLRenderer(4820): Enabling debug mode 0
05-01 20:06:54.536: D/dalvikvm(4820): GC_CONCURRENT freed 170K, 4% free 7509K/7808K, paused 4ms+10ms, total 38ms
05-01 20:06:59.976: D/AndroidRuntime(4820): Shutting down VM
05-01 20:06:59.976: W/dalvikvm(4820): threadid=1: thread exiting with uncaught exception (group=0x40cde930)
05-01 20:06:59.976: E/AndroidRuntime(4820): FATAL EXCEPTION: main
05-01 20:06:59.976: E/AndroidRuntime(4820): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gabilheri.marcuscalculatorv2/com.gabilheri.marcuscalculatorv2.FormulasList}: java.lang.NullPointerException
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.os.Handler.dispatchMessage(Handler.java:99)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.os.Looper.loop(Looper.java:137)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-01 20:06:59.976: E/AndroidRuntime(4820): at java.lang.reflect.Method.invokeNative(Native Method)
05-01 20:06:59.976: E/AndroidRuntime(4820): at java.lang.reflect.Method.invoke(Method.java:511)
05-01 20:06:59.976: E/AndroidRuntime(4820): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-01 20:06:59.976: E/AndroidRuntime(4820): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-01 20:06:59.976: E/AndroidRuntime(4820): at dalvik.system.NativeStart.main(Native Method)
05-01 20:06:59.976: E/AndroidRuntime(4820): Caused by: java.lang.NullPointerException
05-01 20:06:59.976: E/AndroidRuntime(4820): at com.gabilheri.marcuscalculatorv2.FormulasList.onCreate(FormulasList.java:30)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.Activity.performCreate(Activity.java:5104)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-01 20:06:59.976: E/AndroidRuntime(4820): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-01 20:06:59.976: E/AndroidRuntime(4820): ... 11 more
答案 0 :(得分：0)
尝试移动 的setContentView（R.layout.activity_formulas）; 到方法的开始。在超级电话之后。
您正在尝试在初始化活动布局
之前使用gui控件