二维码扫描怎么调用

[panyihu]

public void PressTrsSaoMiao()
{
PressSaoMiao=(Button)this.findViewById(R.id.saomiaobtn);
PressSaoMiao.setOnClickListener(new OnClickListener()
{
public void onClick(View v)
{
Intent mIntent = new Intent();
ComponentName comp = new ComponentName("com.google.zxing.client.android",
"com.google.zxing.client.android.CaptureActivity");
mIntent.setComponent(comp);
mIntent.setAction("android.intent.action.MAIN");

startActivity(mIntent);
}
});
}
为什么点击BUTTON后不能运行二维码扫描程序，求指教