新手android 开发 错误集锦（持续更新中）

（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);

}