How to stop the "force close" error

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http://stackoverflow.com – Iam giving some Values in EditText,but if i try to delete it using backspack button and to enter new value..It is getting ForceClosed.How to Rectify this Problem My code is given below empty_cyl_recvd = (EditText) findViewById(R.id.empty_cyl_recvd); new_cyl_recvd = (EditText) findViewById(R.id.new_cyl_recvd); filled_cyl_unload = (EditText) findViewById(R.id.filled_cyl_unload);`enter code here` dmg_cyl_recvd = (EditText) findViewById(R.id.dmg_cyl_recvd); total_dmg_cyl=(EditText)findViewById(R.id.sdff); total_empty_cyl=(EditText)findViewById(R.id.wertyu); total_fil (HowTos)