新手android 开发 错误集锦（持续更新中） 博客分类： java android javaandroid
（1）error opening trace file: No such file or directory (2)
这是写的第一个程序就出现的问题，而且查询代码没有发现错误。google后得出结论：模拟器版本和android的API版本不对应，相应的进行修改就行。
（2）出现java.lang.NumberFormatException: unable to parse 'null' as integer
出现问题查出错误出在上面代码中intent传回来的值有可能是null，就会产生转换的错误，最终修改方案是加入异常处理机制，就是使用try and catch。修改后程序运行正常。代码如下：
public class otheractivity extends Activity{
private TextView textview2 = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_other);
textview2 = (TextView)findViewById(R.id.TextView2);
int oneint = 0;
int twoint = 0;
Intent intent2 = getIntent();
String onestr = intent2.getStringExtra("one");
String twostr = intent2.getStringExtra("two");
try{
oneint = Integer.parseInt(onestr);
}
catch(Exception e){}
try{
twoint = Integer.parseInt(twostr);
}
catch (Exception e) {
// TODO: handle exception
}
int res = oneint + twoint;
String resstr = String.valueOf(res);
textview2.setText(resstr);
}
}
问题就迎刃而解了。
（3）用一个监听器实现多个按钮的onclick监听。
示例代码如下：
public class SensorActivity extends Activity {
private Button button1 = null;
private Button button2 = null;
private Button button3 = null;
private Button button4 = null;
private Button button5 = null;
private Button button6 = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sensor);
button1 = (Button)findViewById(R.id.button1);
button2 = (Button)findViewById(R.id.button2);
button3 = (Button)findViewById(R.id.button3);
button4 = (Button)findViewById(R.id.button4);
button5 = (Button)findViewById(R.id.button5);
button6 = (Button)findViewById(R.id.button6);
button1.setOnClickListener(new MyButtonlistener());
button2.setOnClickListener(new MyButtonlistener());
button3.setOnClickListener(new MyButtonlistener());
button4.setOnClickListener(new MyButtonlistener());
button5.setOnClickListener(new MyButtonlistener());
button6.setOnClickListener(new MyButtonlistener());
}
class MyButtonlistener implements OnClickListener {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
int i[] = new int[6];
for(int j = 0;j<6;j++){
i[j]=j;
}
HashMap<Button,Integer> bf = new HashMap<Button, Integer>(6);
bf.put(button1, i[0]);
bf.put(button2, i[1]);
bf.put(button3, i[2]);
bf.put(button4, i[3]);
bf.put(button5, i[4]);
bf.put(button6, i[5]);
//Intent intent[] = new Intent[6];
Intent intent1 = new Intent();
Intent intent2 = new Intent();
Intent intent3 = new Intent();
Intent intent4 = new Intent();
Intent intent5 = new Intent();
Intent intent6 = new Intent();
//intent[0].setClass(SensorActivity.this, Sensor1.class);
//intent[1].setClass(SensorActivity.this, Sensor2.class);
//intent[2].setClass(SensorActivity.this, Sensor3.class);
//intent[3].setClass(SensorActivity.this, Sensor4.class);
//intent[4].setClass(SensorActivity.this, Sensor5.class);
//intent[5].setClass(SensorActivity.this, Sensor6.class);
intent1.setClass(SensorActivity.this, Sensor1.class);
intent2.setClass(SensorActivity.this, Sensor2.class);
intent3.setClass(SensorActivity.this, Sensor3.class);
intent4.setClass(SensorActivity.this, Sensor4.class);
intent5.setClass(SensorActivity.this, Sensor5.class);
intent6.setClass(SensorActivity.this, Sensor6.class);
Button button = (Button)v;
int num = bf.get(button);
switch (num) {
case 0:
SensorActivity.this.startActivity(intent1);
break;
case 1:
SensorActivity.this.startActivity(intent2);
break;
case 2:
SensorActivity.this.startActivity(intent3);
break;
case 3:
SensorActivity.this.startActivity(intent4);
break;
case 4:
SensorActivity.this.startActivity(intent5);
break;
case 5:
SensorActivity.this.startActivity(intent6);
break;
default:
break;
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
menu.add(0, 1, 1, R.string.exit);
menu.add(0, 2, 2, R.string.about);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
if(item.getItemId()==1){
finish();
}
return super.onOptionsItemSelected(item);
}
}
关键在于用hashmap将控件与整数对应，然后进行选择。
（4）在同一个activity中使用两个或两个以上的传感器。
在同一个activity中使用多个传感器时，只需要声明一个sensormanager就可以了。但是每个传感器实例都需要单独声明。
监听器可以只使用一个监听器。
具体示例如下：（以两个传感器为例）
private SensorManager sm_gyroscope;
private Sensor my_gyroscope;
private Sensor my_rotation;
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.sensor4)
sm_gyroscope = (SensorManager)getSystemService(SENSOR_SERVICE);
my_gyroscope = sm_gyroscope.getDefaultSensor(Sensor.TYPE_GYROSCOPE);
my_rotation = sm_gyroscope.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);
}
private class Mysensorlistener implements SensorEventListener{
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
int temp1 = 0,temp2 = 0;
@Override
public void onSensorChanged(SensorEvent event) {
// TODO Auto-generated method stub
if(event.sensor.getType() == Sensor.TYPE_GYROSCOPE){
//此处添加代码
}
}
if(event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR){
//此处添加代码
}
}
}
}
Mysensorlistener mylistener = new Mysensorlistener();
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
sm_gyroscope.unregisterListener(mylistener);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
sm_gyroscope.registerListener(mylistener, my_gyroscope, SensorManager.SENSOR_DELAY_NORMAL);
sm_gyroscope.registerListener(mylistener, my_rotation, SensorManager.SENSOR_DELAY_NORMAL);
}
